diff --git a/components/Credential.yml b/components/Credential.yml
index ec1246c..d35e5ea 100644
--- a/components/Credential.yml
+++ b/components/Credential.yml
@@ -91,7 +91,10 @@ components:
           description: The subject
         "proof":
           type: object
-          description: An optional proof for credentials that are secured using proof sets or chains.
+          description: >
+            An optional proof or array of proofs for credentials that are secured using proof sets or chains. 
+            When present, the issuer instance configuration determines how these existing proofs are processed 
+            (appended to create proof sets/chains, or trigger an error).
           oneOf: 
             - type: object
             - type: array
diff --git a/index.html b/index.html
index 7c7742e..5d247ac 100644
--- a/index.html
+++ b/index.html
@@ -902,13 +902,33 @@ <h4>Issue Credential</h4>
 provided `credential`, the instance MUST attach all of these proofs in response to
 a single call to the `/credentials/issue` endpoint.
         </p>
-        <p>
+       <p>
 If a provided `credential` already contains one or more proofs,
-an issuing instance SHOULD append its proofs to the list of existing proofs
-provided by the caller, converting a single proof value to an array of
-proof values if necessary. An issuing instance MAY be configured to return an
-error if `credential` values that contain existing `proof` values are provided.
-        </p>
+the behavior is determined by the configuration of the issuer instance. An issuing 
+instance SHOULD be configured to handle existing proofs in one of the following ways:
+      </p>
+      <ul>
+        <li>
+          <strong>Proof Sets</strong>: Append new proofs to the list of existing proofs 
+          provided by the caller, first converting any existing single proof to a list 
+          if necessary. Here there is no binding to any existing proofs; the new proofs 
+          exist in parallel with those previously provided by the caller.
+        </li>
+        <li>
+          <strong>Proof Chains</strong>: Append new proofs to create or extend an existing 
+          proof chain. Here proofs are linked in a specific sequence, potentially using the 
+          <code>previousProof</code> property to establish the chain relationship.
+        </li>
+        <li>
+          <strong>Error Handling</strong>: Return an error if <code>credential</code> 
+          values that contain existing <code>proof</code> values are provided, when 
+          the instance is configured to only accept credentials without existing proofs.
+        </li>
+      </ul>
+      <p>
+The specific approach used depends on the configuration of the issuer instance and 
+the intended use case for the verifiable credential.
+      </p>
       </section>
 
       <section>