once your sure of the calculations inputs and results. you can go to the tools at the top of the program and select cfm calculation. you must know the amount of CFM /tons cooling size. an axample type in 1200 cfm for 3 tons and it will tell you according to the calculations where the cfms should be per rooms. add the ductwork one time to the program input .Adding the people the way i explained it was how it was explained to me by the company who sells the program.I have been faithfully useing this program on every single job for 3 years now.I will admit that I have not derated any of my jobs. and have had very satisfyed customers. This was something I overlooked until recently reading the threads on the issue. maybe in jersey it was not as crucial.maybe when wall inputs I allway leave blank the exterier sideing type insulations and only input R value in the walls.