Update api-management-howto-properties.md

Author: anjalidivitha

articles/api-management/api-management-howto-properties.md

@@ -42,7 +42,8 @@ Using key vault secrets is recommended because it helps improve API Management s
 * Secrets stored in key vaults can be reused across services
 * Granular [access policies](/azure/key-vault/general/security-features#privileged-access) can be applied to secrets
 * Secrets updated in the key vault are automatically rotated in API Management. After update in the key vault, a named value in API Management is updated within 4 hours. You can also manually refresh the secret using the Azure portal or via the management REST API.
-
+ > [!NOTE]
+    The secrets stored in Azure Key Vault must be between 1 and 4096 characters, as API Management cannot retrieve values that exceed this limit.
 ## Prerequisites
 
 * If you have not created an API Management service instance yet, see [Create an API Management service instance](get-started-create-service-instance.md).