I've never personally owned one of these types of turrets, but they're usually a basic ratchet setup.

You tell the controller what the initial position is. It then moves a set number of steps to go slightly past the required tool position to ensure the ratchet drops over the required pawl, then reverses so the turret tightens against the pawl. Some will then keep running in reverse at reduced power to ensure the turret remains located, while some will stop running and rely on cutting forces to remain tight against the pawl.