Well it’s a big thing, whatever it is!

13,000lb of fuel (about six tons) is quite a lot and surely not in a single tank.

Why the two scales 0-5 and 0-13? Is there a switch that gives a ‘full-scale’ reading for the last 5000lb for more accuracy?

Having said that if you’re worried about how fast you are using your last 5000lb of fuel it must be from a jet. 😀