shadango,
12:00, 1:30, 3:00, 4:30, 6:00, 7:30, 9:00, 10:30 would refer to the position in increments of 1/8 turns.
1:00, 4:00, 7:00 and 10:00 would would certainly have worked fine to communicate what we were doing here. But we're so darn precise, we throw in the '' 30 ''. LOL!