As for Smoothness:
For some mouse which can not provide stable output, or some low dpi mouse,
users can use this feature to make a compensation.
so they can get a more stable control for the cursor.
And this feature might be some helpful for scoped aiming,
some small shakes from mouse or hands can be removed by it.
Or this will also be some help for vehicle(tank/plane) control, circular menu.
But if it is set too high,
users will feel some delay.
0~10 will be ok.