The two square pots located on the circuit board are called out as Switch 1 and Switch 2. In the instructions for the distributor is this sheet that indicates pot positions to determine the actual ignition curve. There are four total electronic centrifugal advance curves and each one of these total curves (10, 15, 20, and 25 degrees of advance) has options for four different rates of advance to achieve those totals. Then there is a total of five different “vacuum” or part throttle advance curves also to choose from. At part throttle, these add to the centrifugal curves. At wide-open throttle, the vacuum curves do not add timing.