I just bought a case (4 gals) of Liquid Chlorine from Rural King for $10.00. The label reads as follows: Available Chlorine - 15%. Sodium Hypochlorite - 12.5%. Which description do I use when adding Chlorine to my pool? Is it 15% or the 12.5%. Second Question: The pool calculator lets me input the 15% reading up in the FC column, but it does not give me the 15% option down in the "Effects of adding chemicals"; thus, I am assuming that I should use the Available Chlorine option at the 12.5% instead of the 15% - is this a correct assumption?