diff --git a/developer_docs/git/commit-conventions.md b/developer_docs/git/commit-conventions.md
index a737f095872..2dbd244c44b 100644
--- a/developer_docs/git/commit-conventions.md
+++ b/developer_docs/git/commit-conventions.md
@@ -19,3 +19,23 @@ Co-Authored-By: Claude <noreply@anthropic.com>
 
 ## Auto-Close Behavior
 When Claude pushes commits that complete an issue, automatically include the appropriate closing keyword in the commit message.
+
+## Branch Naming Conventions
+
+### Hotfix Branches
+When creating hotfix branches targeting production branches (e.g., `ruhunu-prod`), the branch name **must** end with `-hotfix`. This is required for the PR to be mergeable.
+
+**Format:** `<issue-number>-<description>-hotfix`
+
+**Examples:**
+- `19635-configurable-bill-serial-digits-hotfix`
+- `19500-fix-grn-return-hotfix`
+
+### Feature Branches
+Feature branches should be based on `origin/development` (never `master`) and follow the pattern:
+
+**Format:** `<issue-number>-<description>`
+
+**Examples:**
+- `19635-configurable-bill-number-serial-digits`
+- `19500-fix-grn-return-approval`
diff --git a/src/main/java/com/divudi/bean/common/ConfigOptionApplicationController.java b/src/main/java/com/divudi/bean/common/ConfigOptionApplicationController.java
index eaf3984dad6..5202167cf9d 100644
--- a/src/main/java/com/divudi/bean/common/ConfigOptionApplicationController.java
+++ b/src/main/java/com/divudi/bean/common/ConfigOptionApplicationController.java
@@ -215,6 +215,7 @@ private void loadPharmacyConfigurationDefaults() {
         // Future development: Apply these patterns to additional bill types as needed
 
         getShortTextValueByKey("Bill Number Delimiter", "/");
+        getIntegerValueByKey("Bill Number Serial Digit Count", 6);
 
         // Generic bill numbering strategies (for backward compatibility)
         getBooleanValueByKey("Bill Number Generation Strategy for Department ID is Prefix Dept Ins Year Count", false);
diff --git a/src/main/java/com/divudi/ejb/BillNumberGenerator.java b/src/main/java/com/divudi/ejb/BillNumberGenerator.java
index f7c64d82e2b..7d3bd43a1bc 100644
--- a/src/main/java/com/divudi/ejb/BillNumberGenerator.java
+++ b/src/main/java/com/divudi/ejb/BillNumberGenerator.java
@@ -139,6 +139,17 @@ private String getLockKey(Institution institution) {
         return institution.getId() + "-" + "null" + "-" + "null";
     }
 
+    private static final int MAX_SERIAL_DIGITS = 12;
+
+    private String formatSerialNumber(Long serialNumber) {
+        Integer digits = configOptionApplicationController.getIntegerValueByKey("Bill Number Serial Digit Count", 6);
+        if (digits == null || digits < 1) {
+            digits = 6;
+        }
+        digits = Math.min(digits, MAX_SERIAL_DIGITS);
+        return String.format("%0" + digits + "d", serialNumber);
+    }
+
     private String getBillNumberDelimiter() {
         String delimiter = configOptionApplicationController.getShortTextValueByKey("Bill Number Delimiter", "/");
         if (delimiter == null) {
@@ -2160,7 +2171,7 @@ public String departmentBillNumberGeneratorYearly(Department dep, BillTypeAtomic
 
         // Append formatted 6-digit bill number
         result.append(getBillNumberDelimiter());
-        result.append(String.format("%06d", dd)); // Ensure bill number is always six digits
+        result.append(formatSerialNumber(dd)); // Ensure bill number is always six digits
 
         // Return the formatted bill number
         return result.toString();
@@ -2220,7 +2231,7 @@ public String departmentRequestNumberGeneratorYearly(Department dep, RequestType
         result.append(getBillNumberDelimiter());
         
         // Append formatted 6-digit bill number
-        result.append(String.format("%06d", dd)); // Ensure bill number is always six digits
+        result.append(formatSerialNumber(dd)); // Ensure bill number is always six digits
 
         // Return the formatted bill number
         return result.toString();
@@ -2263,7 +2274,7 @@ public String departmentBillNumberGeneratorYearlyWithPrefixDeptInsYearCount(Depa
         result.append(String.format("%02d", year)); // Ensure year is always two digits
         result.append(getBillNumberDelimiter());
         // Append formatted 6-digit bill number
-        result.append(String.format("%06d", dd)); // Ensure bill number is always six digits
+        result.append(formatSerialNumber(dd)); // Ensure bill number is always six digits
         // Return the formatted bill number
         return result.toString();
     }
@@ -2305,7 +2316,7 @@ public String departmentBillNumberGeneratorYearlyWithPrefixInsDeptYearCount(Depa
         result.append(String.format("%02d", year)); // Ensure year is always two digits
         result.append(getBillNumberDelimiter());
         // Append formatted 6-digit bill number
-        result.append(String.format("%06d", dd)); // Ensure bill number is always six digits
+        result.append(formatSerialNumber(dd)); // Ensure bill number is always six digits
         // Return the formatted bill number
         return result.toString();
     }
@@ -2345,7 +2356,7 @@ public String departmentBillNumberGeneratorYearlyWithPrefixInsYearCount(Departme
         result.append(String.format("%02d", year)); // Ensure year is always two digits
         result.append(getBillNumberDelimiter());
         // Append formatted 6-digit bill number
-        result.append(String.format("%06d", dd)); // Ensure bill number is always six digits
+        result.append(formatSerialNumber(dd)); // Ensure bill number is always six digits
         // Return the formatted bill number
         return result.toString();
     }
@@ -2382,7 +2393,7 @@ public String institutionBillNumberGeneratorYearlyWithPrefixInsYearCount(Departm
         int year = Calendar.getInstance().get(Calendar.YEAR) % 100; // Get last two digits of year
         result.append(String.format("%02d", year)); // Ensure year is always two digits
         // Append formatted 6-digit bill number
-        result.append(String.format("%06d", dd)); // Ensure bill number is always six digits
+        result.append(formatSerialNumber(dd)); // Ensure bill number is always six digits
         // Return the formatted bill number
         return result.toString();
     }
@@ -2496,7 +2507,7 @@ public String departmentBillNumberGeneratorYearlyWithPrefixInsYearCountInstituti
         result.append(String.format("%02d", year)); // Ensure year is always two digits
         result.append(getBillNumberDelimiter());
         // Append formatted 6-digit bill number
-        result.append(String.format("%06d", dd)); // Ensure bill number is always six digits
+        result.append(formatSerialNumber(dd)); // Ensure bill number is always six digits
         // Return the formatted bill number
         return result.toString();
     }
@@ -2536,7 +2547,7 @@ public String institutionBillNumberGeneratorYearlyWithPrefixInsYearCountInstitut
         result.append(String.format("%02d", year)); // Ensure year is always two digits
         result.append(getBillNumberDelimiter());
         // Append formatted 6-digit bill number
-        result.append(String.format("%06d", dd)); // Ensure bill number is always six digits
+        result.append(formatSerialNumber(dd)); // Ensure bill number is always six digits
         // Return the formatted bill number
         return result.toString();
     }
@@ -2626,7 +2637,7 @@ public String departmentBillNumberGeneratorYearly(Department dep, List<BillTypeA
         result.append(getBillNumberDelimiter());
         result.append(String.format("%02d", year));
         result.append(getBillNumberDelimiter());
-        result.append(String.format("%06d", dd));
+        result.append(formatSerialNumber(dd));
 
         String finalResult = result.toString();
         return finalResult;
@@ -2677,7 +2688,7 @@ public String departmentBatchBillNumberGeneratorYearlyForInpatientAndOpdServices
         result.append(getBillNumberDelimiter());
         result.append(String.format("%02d", year));
         result.append(getBillNumberDelimiter());
-        result.append(String.format("%06d", dd));
+        result.append(formatSerialNumber(dd));
 
         String finalResult = result.toString();
         return finalResult;
@@ -2728,7 +2739,7 @@ public String departmentIndividualBillNumberGeneratorYearlyForInpatientAndOpdSer
         result.append(getBillNumberDelimiter());
         result.append(String.format("%02d", year));
         result.append(getBillNumberDelimiter());
-        result.append(String.format("%06d", dd));
+        result.append(formatSerialNumber(dd));
 
         String finalResult = result.toString();
         return finalResult;
@@ -2816,7 +2827,7 @@ public String departmentBillNumberGeneratorYearly(Department dep, Department bil
 
         // Append formatted 6-digit bill number
         result.append(getBillNumberDelimiter());
-        result.append(String.format("%06d", dd)); // Ensure bill number is always six digits
+        result.append(formatSerialNumber(dd)); // Ensure bill number is always six digits
 
         // Return the formatted bill number
         return result.toString();
@@ -2877,7 +2888,7 @@ public String departmentBillNumberGeneratorYearlyByFromDepartmentAndToDepartment
 
         // Append formatted 6-digit bill number
         result.append(getBillNumberDelimiter());
-        result.append(String.format("%06d", dd)); // Ensure bill number is always six digits
+        result.append(formatSerialNumber(dd)); // Ensure bill number is always six digits
 
         // Return the formatted bill number
         return result.toString();
@@ -2936,7 +2947,7 @@ public String departmentBillNumberGeneratorYearly(Department dep, BillTypeAtomic
 
         // Append formatted 6-digit bill number
         result.append(getBillNumberDelimiter());
-        result.append(String.format("%06d", dd)); // Ensure bill number is always six digits
+        result.append(formatSerialNumber(dd)); // Ensure bill number is always six digits
 
         // Return the formatted bill number
         return result.toString();
@@ -2978,7 +2989,7 @@ public String departmentBillNumberGeneratorYearly(Institution ins, Department de
 
             // Append formatted 6-digit bill number
             result.append(getBillNumberDelimiter());
-            result.append(String.format("%06d", dd));
+            result.append(formatSerialNumber(dd));
 //        billNumber.setLastBillNumber(dd);
 //        billNumberFacade.editAndFlush(billNumber);
             // Ensure bill number is always six digits
@@ -3005,7 +3016,7 @@ public String departmentBillNumberGeneratorYearly(Institution ins, Department de
 
             // Append formatted 6-digit bill number
             result.append(getBillNumberDelimiter());
-            result.append(String.format("%06d", dd)); // Ensure bill number is always six digits
+            result.append(formatSerialNumber(dd)); // Ensure bill number is always six digits
 
             // Return the formatted bill number
             return result.toString();
@@ -3392,7 +3403,7 @@ public String cashierSettlementBillNumberGeneratorYearlyWithPrefixDeptInsYearCou
         int year = Calendar.getInstance().get(Calendar.YEAR) % 100;
         result.append(String.format("%02d", year));
         result.append(getBillNumberDelimiter());
-        result.append(String.format("%06d", dd));
+        result.append(formatSerialNumber(dd));
 
         return result.toString();
     }
@@ -3434,7 +3445,7 @@ public String cashierSettlementBillNumberGeneratorYearlyWithPrefixInsDeptYearCou
         int year = Calendar.getInstance().get(Calendar.YEAR) % 100;
         result.append(String.format("%02d", year));
         result.append(getBillNumberDelimiter());
-        result.append(String.format("%06d", dd));
+        result.append(formatSerialNumber(dd));
 
         return result.toString();
     }
@@ -3475,7 +3486,7 @@ public String cashierSettlementBillNumberGeneratorYearlyWithPrefixInsYearCountIn
         int year = Calendar.getInstance().get(Calendar.YEAR) % 100;
         result.append(String.format("%02d", year));
         result.append(getBillNumberDelimiter());
-        result.append(String.format("%06d", dd));
+        result.append(formatSerialNumber(dd));
 
         return result.toString();
     }
@@ -3516,7 +3527,7 @@ public String cashierSettlementInsIdGeneratorYearlyWithPrefixInsYearCountInstitu
         int year = Calendar.getInstance().get(Calendar.YEAR) % 100;
         result.append(String.format("%02d", year));
         result.append(getBillNumberDelimiter());
-        result.append(String.format("%06d", dd));
+        result.append(formatSerialNumber(dd));
 
         return result.toString();
     }
diff --git a/src/main/java/com/divudi/ws/common/ConfigResource.java b/src/main/java/com/divudi/ws/common/ConfigResource.java
index 79e3f109e97..0cacc82427d 100644
--- a/src/main/java/com/divudi/ws/common/ConfigResource.java
+++ b/src/main/java/com/divudi/ws/common/ConfigResource.java
@@ -73,6 +73,20 @@ public Response setLongTextValue(@PathParam("key") String key,
         return successResponse();
     }
 
+    @POST
+    @Path("setInteger/{key}/{value}")
+    @Produces(MediaType.TEXT_PLAIN)
+    public Response setIntegerValue(@PathParam("key") String key,
+            @PathParam("value") int value,
+            @Context HttpHeaders headers) {
+        String apiKey = headers.getHeaderString("Config");
+        if (!apiKeyController.isValidKey(apiKey)) {
+            return unauthorizedResponse();
+        }
+        configOptionApplicationController.setIntegerValueByKey(key, value);
+        return successResponse();
+    }
+
     private Response successResponse() {
         return Response.ok("Configuration updated successfully.").build();
     }