I understand that you need to add more chlorine when CYA is high to get to a particular FC level. However, I thought the FC level to attain was still around 5 or so. My TFP android app always says recommended FC between 2.0-6.0 independent of CYA level., But below chart is totally contradictory, i.e. recommend much higher levels based on CYA Pool School - Chlorine / CYA Chart