In the case of backlash control, it has to overcome a deadband. The deadband comes into play when the focuser changes direction. During the focus routine, it typically slowly moves the focuser inwards, creating the V curve and then, having calculated the right position, moves back out to that point. The problem is, with backlash, it moves to the incorrect physical focuser position, though the stepper motor will be right. You effectively remove this deadband by always making the final move in one direction only, typically inwards, against gravity.
Let’s say the focuser has moved from 1000 to 800 during the V-curve and needs to move back out to 900 for the right position. If the backlash is 50 units, it will only get to 850. The trick is to move it further out, by more than 50 units and then return by the same amount, ensuring the mechanism is engaged. In this case, if the backlash setting is more than 50 units, say 70, it will guarantee that the final move of 70 units inwards, actually moves the focus tube. For refractor units, most of us would select IN, as the final movement, as it is against gravity and ensures the mechanism is fully engaged. SCT users, moving mirrors, may do something different.