step adjustment

hi , how do i adjust me steps.  eg..when i do  20 x20 box  it measures  18.5  and the z  is out as well,  target depth  for  10mm  is only going  8.mm and stops

thanks  Ken from Tasmania

If you want to set the scales empirically, you could set
the joint 0 and joint 1 step scales to their current value *18.5/20
and the joint 3 step scale to its current value * 8/10.