Peter,
I quickly found that the 8Mb SD card that was supplied with the KN7000 was entirely too small for a performing musicion. I bought a 128Mb card which seems to have sufficient capacity at this time.
Since the number of files that can be stored depends upon what type of files you store, I'll give you an example of what I have on my card so far.

1. 800 .CST single custom files from the KN7000 web site plus others.

2. 63 .AST 20 song custom files.

3. 111 performance song files. Most of these do not have the sequencer saved.

4. No MIDI or music files.

For the above, 51Mb is used out of a total storage capability of 120Mb.
I hope that this gives you some guidance.
Regards,
Walt