What do the different columns mean?
It is a scalable recipe. First, you decide in which pan you want to bake the cake. You take your pan and measure it. Let's say you have a 9" round pan. You go into the column "lbs per round" and find out that your pan takes 3 1/2 lbs of batter. Then you go to the other table with ingredients measurements, multiply the column "6 lbs" by 7/12, and have your ingredient measurements. Alternatively, you can bake a slightly thinner cake, and divide the amounts in the 6 lbs cake by 2.
Alternatively, if you want the tall kind of cake shown in the pictures, first decide what amount you want to bake, then use the table to calculate how many pans you will need to get that amount of batter baked. For example, for a 8 lb cake with a square base, you could use 4 6" square pans.
When you have made your batter, the last column tells you how much time you should expect, roughly, for the cake to bake through. For the 9" round cake, it would be 1 hour 10 min. Don't forget that this is only an estimate, you should take the cake out when it is done, not when the timer goes off.
Just measure across the pan. If the pan is round then use the round column. If the pan is square then use the square column. Baking time is exactly that.
If the pan is not square (and not round) then not perfect but use the average. So for a 5 x 7 rectangle then use 6.