Hi,
i think it is based on your step resolution (but dont know 100%)
320 steps per mm means a resolution of 0,003125mm
Mach can only do one step, so if i does one step more:
0,0094 + 0,003125 = 0,012525 or in the other way
a move of 0.01 would be 3.2 steps
0,250 would be 8 step's and so on.
Thomas