hi,
the 'b-stage' is the catwalk into the crowd, the 'c-stage' was further away, on a small stage somewhere in the middle of the crowd.
To add such details 'in grey', you put "@Set[b-stage]" or something similar, above the songs, and just "@Set" after the last song of the special set. Take a look at the guidelines for more detailed information: http://www.setlist.fm/guidelines
Rock on!

Thx Riazor