[MrFlippant]

I was asked to work out the actual change in dimension according to the indicator knob. Here's the math: 

The 1/4-20 bolt is 20 threads per inch, so thread pitch is 1/20" (0.05" or 1.27mm). 
The ratio of center points (axle and knob pivot) to the axle bracket pivot point is 1.226, so the wheels move that much more than the knob does.
Multiply 1.27mm by 1.226 and we get 1.55mm per full knob rotation, or 0.13mm per whole number. 
There are 72 notches, so each notch would be 0.0215mm.