Update alert.md

Author: jlichwa

articles/key-vault/general/alert.md

@@ -162,7 +162,9 @@ If you followed all of the preceding steps, you'll receive email alerts when you
 
 ### Example: Log query alert for near expiry certificates
 
-You can set an alert to notify you about certificates which are about to expire.
+You can set an alert to notify you about certificates which are about to expire. 
+> [!NOTE]
+> Near expiry events for certificates are logged 30 days before expiration.
 
 1. Go to **Logs** and paste below query in query window