I just had this same issue in the desktop software. It actually does create more than three boxes, but they are sort of hidden. There is a very hard to see "scroll bar" on the right side. Use your mouse wheel to scroll down and you will see more boxes to enter these codes. It is REALLY HARD to see and the window continues to just show three entry boxes. Running on a MAC as well, FYI.
Another note on this - MAC software seems to crash a lot on this page depending on how/where you click off these boxes.
