Minor issue with manual recording

When I submit a manual recording, I'm using an example found on the forum. Mine contains the line:
"Source": "Manual",

No matter what I put in for source, it produces an error in the log file:
"[ERR] Unknown source for raw airing:".

Is there any value I can put in that does not produce a log file error?

The recording still happens, but I prefer not to have misleading errors in the log file.

That's normal. It just means it doesn't know any guide provider named 'manual' to verify the show information.