River,

When the temps get to 55 degrees or colder, the output will automatically reduced to 1%, and cannot be increased but can be lowered to 0% (off).
As temps fall, this compensation feature automatically adjusts the output so you don't have to. In cold temp conditions, lowering the output helps save the cell life. You don't have to shut it off and revert to hand feeding chlorine. Cold temps require very little chlorine.

The Automatic Temperature Compensation is not adjustable in sensitivity and is in the software.
As the temps change 5 degrees, it adjusts 25% of the setting.
your pool is a perfect example: At 80 degrees, and 50% setting, when it dropped to 75 degrees, the output dropped 25% of 50% (or 12.5%) to 37.5%.

I would set the output to 60% and monitor it. The temp adjust would have dropped it to 45% instead of 37.5%.

Hope this helps