My Audi head unit only shows 99 playlists once you get to 100 the display shows 01 & goes on but with the voice indexing its not really a limitation.
A "disc" on the PhatBox represents a particular playlist as organized in the software component of the system. The PhatBox can have the headunit recognize up to 10,000(!) discs. Each disc can contain up to 10,000 tracks (songs), identified by "rolling over" the two-digit display on the headunit. You can also access these tracks and discs via the remote control that comes with most high-end headunits. And no, those aren't typos. =)
The phatbox Is one of the best things I have bought
I upgraded the hard drive using phathac now my entire CD collection is in my car so I just leave it on random play & do not listen to the radio any more.