Finger trouble: sounds like they made a keying error that ultimately indicated they had less fuel than they were supposed to have. And that they figured it out and corrected it.

Talking about fuel, it's time to link to one of my favourite internet reads. Captain Dave flies A319s, -20s, and -21s. If you look at his posts over a long period of time, you'll see that he spends a lot of time thinking about fuel. He worries about it and frequently uses a steam-driven pencil to double check the "Electric Jet's" computer. Just browse down through a few posts:

http://flightlevel390.blogspot.com