I'm creating a table (for "fun") using excel to calculate the amount of FC increase for various pump run times and % levels of my SWG. Treating 1 oz chlorine gas "like" 1 oz of water volume, my numbers were close, but not exact to those of the pool calculator. My SWG puts out 32 oz of chlorine in 24 hours according to the manual. Is there a scale factor I don't know about? Here is my spreadsheet.