emphasize deletion of all signatures if using invalid identity

Author: Jan Wozniak

Diff for: admin_guide/image_signatures.adoc

@@ -124,9 +124,15 @@ $ oc adm policy add-cluster-role-to-user system:image-auditor <user_name>
 endif::[]
 ====
 
+[IMPORTANT]
+====
 Using the `--save` flag on already verified image together with invalid GPG key
-or invalid expected identity causes the saved verification status to be removed,
-and the image will become unverified.
+or invalid expected identity causes the saved verification status and all
+signatures to be removed, and the image will become unverified. 
+
+In order to avoid deleting all signatures by mistake, you can run the command 
+without the `--save` flag first and check the logs for potential issues.
+====
 
 To verify an image signature use the following format: