The question is sensible. The Vari-Eze a canard type aircraft has 3 fuel tanks. The 2 mains in the wings feed together. The 3rd reserve tank,behind the passenger's headrest hardly ever needed to be used and was good for about 30 minutes. It gravity fed the engine so dodgy fuel pumps weren't an issue.
Most Vari-Eze drivers would use up all the fuel in the reserve tank from time to time in order to refresh it. Of course this would be when there was plenty of fuel in the mains.
The reserve tank was a good idea because it was vented separately and fed independently to the mains. Also if anyone ever got down to reserve only they knew exactly how much fuel they had left and knew they needed to get serious about finding somewhere to land.