I don't think the walmart test gives you a free chlorine reading and a combined chlorine reading. I think it says the first reading is your fc, and you wait a little, then read it again - that will give you a combined chlorine. It is not very accurate. You can take a water sample to a pool store, or make an investment in a good test kit. It will pay for itself in the money you save in chemicals when you can accurately test your own water.