We don't have good data on chlorine loss, if you follow the Best Guess chart, at different CYA levels. What seems to be true is, the chlorine loss is similar, regardless of CYA levels. However, at HiC2 levels, you have a much, much larger reservoir of chlorine present, so there's a larger safety factor, if you miss a day or have a pool party. And, at levels around CYA=150 ppm, you can usually dose with chlorine just 1x per week.