Woohoo I won! Cool little game. Played it on Wine without a problem.
I would agree with the first puzzle being hard. I wasn't sure if I simply had the combination wrong, or if I had to press enter / do some other action after entering in the combination in order for it to take effect. I think an easy fix would be to change the order of the puzzles. The briefcase puzzle is easier in that it's more obvious that you need to change the combination somehow. So you'd go through that puzzle first where you're forced to distrust the note, and then on the PIN you'd have some reason to distrust what was written there by example of the briefcase note not being 1 to 1 with the combination.