On the model MT 22, we have a little arm on the right of the machine, close to the tire. You put its end on the rim at the indicated position of the weight and automatically the machine records the diameter and the offset.
The width of the tire, must be added by the technician with the keyboard of the machine, to help him a gauge is supplied, as a caliper, to measure with.
Do this and off you go, perfect balance every time with no chasing weights around the rim.
Hope this helps.
Nick