Currently, you can select an alert if you are going above the speed limit (at all) or 5 mph over the limit.

I would like to suggest 2 mph.

5 mph is too much because by then, a cop will almost surely give a ticket without mercy. 5 mph over the limit is usually the informal grace limit.

But an alert for any mph over the limit is too sensitive. Even on cruise control, my car sometimes exceeds the limit by a fraction of a mph when I begin to go downhill. It takes a second for the cruise control to adjust, but by then, Waze has already beeped at me. So it's too sensitive. 2 mph would be much better.