Hi John
Jeff has generated his MP3 using the B2's FLAC+MP3 compression option, which generates a "hidden" mirror copy of the B2's music.
As it is "hidden" non of the normal B2 functions will work on it so you cant retag it using the B2.
I think the best option would be to plug the USB device with the mirror on it into a PC and run a program like
MP3Tag over it.
Fred