Some designs are written with so many variations or sizings that it's very tricky to write out the individualised instructions. Sometimes the maths depends on the stitch count, and as you, the knitter, are the one that knows that count, the onus then falls to you to work the maths.
I try to help knitters through the maths as best I can, however I know that often you'd prefer the computer to do the work. So my wonderful computer programmer of a husband has written this little widget so that the calculations are done for you. Isn't he ace?