A V8 fires every 90 crank degrees. The time width between pulses varies with RPM. Higher RPM the shorter time between events. A dial back is a way to subdivide time, divide by 90, each division is a degree. Most use a pot to select count of divisions, pots suck, for accuracy.
4 cylinders fire 180d, /6 at 120d so a dial back needs to know that. Nothing to do with balancer diameter, just time delay. An example for V8, 3000 RPM width is 5ms, half of that is 2.5ms, delay that amount for light would be 45 degree setback.
