diff --git a/src/ssrz_blocks.py b/src/ssrz_blocks.py
index 7b26d87..e89e4ad 100644
--- a/src/ssrz_blocks.py
+++ b/src/ssrz_blocks.py
@@ -1560,7 +1560,7 @@ def __init__(self, msg, unpacked_bits, zdf107_bit0=False):
         n_coeff_triangle = compute_ncoeff_from_order_triangle(self.m_hor)
         self.n_coeff = (self.m_hgt + 1) * n_coeff_triangle
         # Compressed coefficients block definition of regional tropo component
-        self.blk = zdb023(msg, unpacked_bits, self.n_coeff)
+        self.blk = zdb023(msg, unpacked_bits, self.m_hor + 1)
         unpacked_bits = self.blk.unpacked_bits
         # Separated compressed coeff block per height
         if zdf107_bit0:
diff --git a/src/ssrz_fields.py b/src/ssrz_fields.py
index 1f3e6e7..29fefc5 100644
--- a/src/ssrz_fields.py
+++ b/src/ssrz_fields.py
@@ -478,11 +478,11 @@ def zdf056(msg, unpacked_bits):
 
 def zdf057(msg, unpacked_bits):
     """ SSR update interval offset of an SSR update interval.
-        T_offset = ZDF057 + 1
+        T_offset = ZDF057
     """
     [pr_code, num, bits_zdf057] = prefix_coding(msg, 6, 0,
                                                 unpacked_bits=unpacked_bits)
-    t_offset = num + 1
+    t_offset = num
     return [t_offset, bits_zdf057]