Have been trying to get my CYA up to 70-75. Tested last week using my Taylor K2006. Dot disappeared around 50ppm. Before adding additional stabilizer, decided to take a water sample to pool store. They tested CYA at 100ppm. When performing my K2006 test, I wait for water temperature in sample bottle to equalize with room/outside temperature before completing test. I'm using a fresh reagent. I don't get why the wide span differential? So now, not sure whether to drain water or simply trust my K2006 reading and add stabilizer to bring up to 70-75ppm.