5 character code - 0-99999 = 100,000 possible codes.
In the flash animation above the video (on the passwindow site), there are clearly more than 5 digits. I can see 16 places a digit can be (counting the _ sections of the digit, the uprights overlap).
If I was able to receive multiple challenges from the server, I would repeat the process and cross compare results. This would allow me to determine the key on the card within an almost 100% accuracy
If I was able to have multiple attempts, I can break any password
"The trouble with doing something right the first time is that nobody appreciates how difficult it was." -- Walt West