Pedantry: when the motor starts moving, it's a fine correction, but after one rotation of one of the gears it hits a stop and changes to a coarse correction. It

Pedantry: when the motor starts moving, it's a fine correction, but after one rotation of one of the gears it hits a stop and changes to a coarse correction. It then continues to do coarse correction as long as you rotate in that one direction. If you reverse the motor, you get fine correction again until that gear turns one rotation and hits the other side of the stop, reverting to coarse correction. Once you have things coarsely aligned, you back the motor a bit and then operate within the single rotation of that gear, staying with fine correction.