Squeak,
I have a hard disk recorder (Roland VSR880) and the time allotted for total recording is AVERAGED out to a "time per track".
I'm not positive, but I think that time is in a lump sum, just waiting to be used, so if you didn't need all 8 tracks - it's very possible to record longer than the average. It only uses ACTUAL time, as far as I know.
At least, that's the way the Roland works.