The amount of games you can add is determined based on the Game Save States. If you want to have all games being able to use 4 save state files at the same time, 32 games is the limit, any more and you get error messages.
If you don't intend to use every single save state block, you can add more. 97 seems to be the magic number. But be aware, the emulator this thing uses is kinda crap, and a lot of games will have issues. I wanted to add Zoda's Revenge, but it can't get past the Name Input screen. Battletoads will always freeze on the 2nd stage. It's due to the emulator, not the hack.
I'd say until more testing is done, and compatibility is confirmed, go slowly and only add games you intend to actually play-through.