It was more confusion. One system was broken, and the alternate was taken out of service. The pilot was then confused because flying with only one sensor was considered acceptable, but he was asking about a both sensors out situation instead. So they did it the old school way with dipsticks, but the conversion formula written on the sheet was wrong because they were in the process of switching. Also, the person who's job it is to get this right didn't exist on the 767 and Air Canada had not finished figuring out how to divvy up the duties when that seat wasn't filled. It's one of those Frogger failures, so many things have to line up just right at this one point in history for the problem to happen. Luckily in this case everyone came out ok.

The fuel gauges were inoperative. Apparently this condition does not ground the plane, however the crew has to maintain awareness of the fuel level via alternate means. on the ground you put a stick in the tank and in flight you know how much fuel was loaded and you know much was burned(airplanes tend to have good fuel per hour meters). Only this time the amount of fuel requested was in gallons and the amount loaded was in liters.....

https://en.wikipedia.org/wiki/Gimli_Glider

But absolute respect to the pilot for getting it down in one piece. I mean on one level he was just doing his job. but sometimes that is all it takes to be a hero, to do your job in the face of adversary.

https://www.youtube.com/watch?v=686xoeQAVA4