How does the bleach calculator help with acid dosing?

I can at least speak to what I do. If my pH reading has shot up to the first high reading, which I believe is 7.8, in my 20,000 gallon pool, a full cup will bring it down into range. If you're unsure, modify according to the size of your pool and cut the amount in half, then retest a few hours later or the next day and see if you're good or need to add a bit more. You will soon learn how much your pool requires to bring it back into range.

Be sure to wear gloves and eye protection, or close your eyes as you're pouring it in in front of your deep end jet. And, hold your breath until you've got the acid jug recapped. And if you can, keep holding your breath while you quickly walk away from the area as the fumes are still in the air; more than just obnoxious, they're dangerous!