Calculating gear ratio for leadscrew
Your lead screw nut advances 8&nbsp;mm every complete rotation of 200 full steps, so a single full step would change the height by 8/200 = 0.04&nbsp;mm. This implies you need to set the layer height a multiple of 0.04&nbsp;mm.

The gear ratio of 4:1 (a reduction) is required to get to your desired 0.01&nbsp;mm layer height, but that is a very uncommon and a too small layer height to use.