What is the "unit" length in Mach? Inches I presume?
Your drive gear has a pitch circle circumference of 3.7699", and it appears as though in your 'lossless system' that your motor turns 2000 microsteps per revolution. So divide the distance by the steps and you get 530.5 steps per inch. Of course, there is no such thing as half a micro step, so you'd have to round up or down, I suppose.
Don't neglect to allow for cutter diameter when milling your 1" square pocket.
First you get good, then you get fast. Then grouchiness sets in.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)