First off my field is Electrical but I am trying to learn every aspect of ABS that I can. I changed the Capacity (CFM) of a main branch of Supply Duct in the Modify Duct dialog box. When I did, the value I entered went from black to red. I did notice when I changed that value, the friction, along with the velocity changed as well. Obviously something is wrong with what I entered. All I did was change the CFM from 1200 to 1600. Can someone please help explain in the area of Mechanical. Thanks!