I've tried about every combination that I can think of, particularly involving modifier keys (used for gaming) and it's always 6 keys? I'm pressing them all simultaneously and they're all lighting up.
EDIT: I take that back, after more playing I have found some (very unlikely used) combinations that will only allow for say, 3 or 4 keys, etc.
Using specific key combinations that I actually use for gaming, such as shift + strafe(a),forward(w),jumping(space), they all register fine. That's probably why I don't have a problem with gaming, I"m just lucky with the key combo that I use.