I presume it is only when doing a move with at least 2 axis that you are seeing that? That is blended speed which is the speed the actual cutter is doing. As an example you are at X0Y0 and you tell the machine to move to X10Y10 the axis will move diagonally and that means the path the cutter takes is longer than the 10 units each axis is moving. As each axis is doing 12IPM then the blended speed will show more.
Hood