TH is a measure of the levels of both calcium and magnesium in your water and is always going to be higher than your calcium hardness. It’s not really a test that will be useful for a pool but many of the less expensive test kits and just about every test strip I have seen test for total hardness and not calcium hardness. If you have a drop-based test and it only uses 2 reagents instead of three it is most likely testing total hardness. This test also changes from pink to blue.
