No need to put anything down in PoolMath.
If 8.0 or higher, add enough muriatic acid to lower the pH by 0.4
Retest in 30 minutes, if still 8.0 or higher, add enough acid to lower it another 0.4
Rinse, repeat.
Once in the 7's, record the pH reading in PoolMath.
Use Affects of Adding in PoolMath...