The correction for CYA does not have a great impact on TA when CYA is in the normal 30-50 ppm range, It work out to about 10-15 ppm. Considering the precsion of the TA test is +/- 10 ppm it really is inconsequential. Even at the higher CYA levels recommended for SWGs the amount of error has no great impact. Only when CYA levels become excessive does the correction for CYA become important and at that point the high CYA is the major problem that needs to be addressed.