The Quark is supposed to be able to detect the number of cells in the pack. The cutoff voltage represents the voltage of each cell that is reached before the LVC will kick in.

This is all fine and dandy, except that the Quark "measures" the voltage of the pack when you first plug it in and then makes a determination of the number of cells based on the voltage that it read. The downside to this is that if you plug in a pack that isn't fully charged, the esc could misread the number of cells in the pack. For example, it could misread a 5S pack as a 4S pack, and then the lvc wouldn't kick in until the pack reached 12v, at which point your 5S pack would be dead, dead, dead.

I don't rely on the voltage cutoff. I have a rough idea of how long my batteries will last on a charge and I just look at my watch when I plug the battery in. Personally, I don't think that the built in lvc on the Quark is of much use anyway. Most of the newer 20C packs really shouldn't be discharged below 3.2v anyway. If you run a 20C lipo pack down until the lvc cuts off, you may have already done some damage. That's my opinion anyway.