The old rule of thumb limit is one pint per 10,000 gallons at a time, perhaps a quart per 10,000 gallons in extreme cases. However, the higher your TA level, the more acid you need to achieve the desired result. If you have a reliable TA reading that shows extremely high TA levels then using more acid at one time makes sense.
When lowering TA you want to target a PH of between 7.0 and 7.2. After a couple of cycles of lowering the PH you should be able to get a sense of how much acid it will take to make a given PH change. Even keeping in mind that the amount of acid you need to use goes down as TA goes down, that will still be more accurate than using the Pool Calculator.