It's very easy, Soc. You can order the burgers however you like, and you leave the patty on the grill for a certain amount of time (clocked), flip it, and do the same for each temperature. The advertised weights are based on medium well since that's the lowest temperature considered "safe" anyway (not that anyone is actually going to get sick eating a medium burger, but you know how it is). And, by the way, if any of you ever come through Indianapolis (or Bloomington, IU campus), there is not a better burger in the world than Bub's. Watch the Man v. Food clip on it if you're curious.
Draug, reading through this thread, I'm absolutely shocked that no one else seems to go with after cooked. I guess I've never really looked at other places for it but now I guess I know why the half pound at Bub's is so much more filling than the half pound at other places...