you motor is 1.8 degrees per step...... so each full step is 1.8 degrees. Now add the micro stepping (10) you get what 5.555 steps per degree? The motor is 200 steps per rev. The steps per in mach 3 is not per revolution, its steps per DEGREE So your settings tell mach to take 4 steps per DEGREE to be able to make a 360 degree rotation.