The kegulator is used to determine how much beer, ice and cups you need given your crowd size and drinking habits. Being able to figure that is out is simply a matter of knowing a few constants, such as how much beer is in a keg. If you start knowing that a 1/2 keg has 7 cases of beer and that a case is equal to 24-12 oz beers, all you need to know is how many people will be there and the average consumption, and you are pretty much done.
Of course, if you are among the percentage that would rate as requiring 10+ beers that night, odds are you have had enough to drink already this evening and doing that simple math is more than you can handle. The real key is knowing how much the average of the group will drink, but that falls more under the the specialty of someone who can see the future rather than a piece of software. It’s not all bad, though, I do applaud the developer for working on a real world problem. If the party host can’t properly plan, the party could be over before it has even begun.