trojan hidden inside app?
I would suggest having the program create a backup of the ticket, before modifying. That was if the method used (+2 or -2) is the incorrect one, then you can just modify the backup using the correct option.
Not too difficult to do this manually in a hex editor, but seeing this was made for noobier people who don't want to edit in hex, that would probably be a good idea.
Edit: also just to say I did test this and it does work properly.
trojan hidden inside app?