soap lye calculator

I have this "calculator lye" thingy on this website. What do they mean by excess fat?
I'm trying soap-making. excess fat% is under the table so that the bleach they mean by that? http://www.thesage.com/calcs/lyecalc2.php psyou website-> must enter the amount of fat and weight measurement units first. so does this mean we need to add extra oil?
Reread the calculator. He says: "We believe that this allows a firm bar with enough excess fat to have a good feeling. Increasing amounts of excess fat are not desirable, as it will shorten the life of the soap and make the very mild soap. soft soap bars in the shower is consumed much faster than a bar signature. "Excess of fat is what makes the bar hard or soft, the lifetime of the telenovela. Does that help? Jj … Depends on the consistency of soap you want. … Jj
Soap Making Books Review/Information