Chem Geek,
No idea either but the acid usage is definetly down, it seems to hold near a pH of 7.4, for most of the day, and might rise to 7.5 or 7.55 overnight, if the pool is uncovered , especially if it is windy, 16 to 24 mph are our normal trade winds, although the other day we had 50+ mph winds. If covered at night the pool pH pretty much holds until uncovered. Each day the required amount of acid is added to compensate for adding liquid chlorine, using PoolEquations spreadsheet recommendations as a guide, plus a little to compensate for risen pH over 7.4 if needed.
I still have not replaced the PoolPilot Digital controller as we had heavy rain up in the mountains where we live, but nice and sunny at the beach down the hill, some 2 1/2 miles (1 1/2 mile as the crow flies), and at Waikiki beach a 5+ mile drive.
This is just for info that might help you determine why the rise in pH is slow, the pool temp was around 75-78F.