Registered: 19/05/1999
Posts: 3457
Loc: Palo Alto, CA
Mostly out of thin air, really. The biggest Mk1 that ever shipped was 20G, so I just doubled it. As various people have said, high bitrates mean a smaller database.
You can check the size of the database, it's in /empeg/var - add the tags, playlists and database sizes together.