Upgrade overrides exporter docs

Signed-off-by: SungJin1212 <[email protected]>

Author: SungJin1212

docs/guides/overrides-exporter.md

@@ -62,3 +62,18 @@ cortex_overrides{limit_name="max_samples_per_query",user="user1"} 100000
 
 With these metrics, you can set up alerts to know when tenants are close to hitting their limits
 before they exceed them.
+
+
+## Exposed Metrics
+Prior to version v1.20.0, the exporter only exposed the fixed, hardcoded list of limits shown in the example section above.
+
+As of version v1.20.0, the exporter automatically discovers and exposes all fields from the [limit_config](../configuration/config-file-reference.md#limits_config) configuration
+that are numerically representable.
+
+The exposes metrics based on the following rules:
+- Numerical types (`int`, `int64`, `uint`, `uint64`, `float64`) are converted directly to a `float64`.
+- bool types are converted to 1.0 (for `true`) or 0.0 (for `false`).
+- model.Duration types (which are internally `int64`) are converted to the total number of seconds as a `float64` (e.g, 1h becomes 3600.0).
+
+Fields with types such as `string`, `slice`, `map`, or other nested structs (like `metric_relabel_configs`) are ignored and not exported as metrics.
+