I had this mouse.
At this mouse different sensitivity for high speed of moving and low.
For example, if to move very slowly that having made in game, the turn of 360 degrees, the mouse on a rug will move on 10 see
If to move very quickly, on 360 degrees the mouse on a pad will move on 20 see
In other words the mouse has negative acceleration!
Moreover the mouse way on a pad with slow speed does not depend on sensitivity of the mouse established in the driver!
Sensitivity in the driver depends on parametre only average and high speed of moving.
In other words if we move the cursor from a screen left edge to right with a great speed, and then we will slowly return to a left edge that the mouse will not return to an start point on to mousepad