In this case, the “angle” is rather easy to calculate, since we are talking about the minute hand. At 10:00, the minute hand is pointing straight up, and at 10:30 it is pointing straight down. So the change in height of the tip is just one diameter of the clock (i.e., twice the radius).
Remember the absolute height doesn’t matter (indeed the potential is defined so it can be shifted by any amount), but the height difference: . You know where .