clarify multiple x tags and bulk mirror

buds/04.md

@@ -23,6 +23,8 @@ Clients MUST set the `Authorization` header to an upload authorization event def
 
 The `/mirror` endpoint MUST download the blob from the specified URL and verify that there is at least one `x` tag in the authorization event matching the sha256 hash of the download blob
 
+**Multiple `x` tags MUST NOT be interpreted as the user requesting a bulk mirror.**
+
 The endpoint MUST return a [Blob Descriptor](#blob-descriptor) if the mirroring was successful or an error object if it was not
 
 Servers should re-use the `Content-Type` header returned from the URL to discover the mime type of the blob. if none is returned it may use the file extension in the URL