Gas tank size on '93 Civic DX hatch ?

[Cd]

The manual says 11.9 gallons, but the tank only seems to hold 10.

I need to find out the exact capacity that the tank is so that I can calibrate my SuperMID correctly.

I suppose I could just drive the car till it runs out of gas and then do a fill up, but from what I have read, this is actually bad for the car.
( Also, the last thing that I want to do is stall with someone behind me. )

So is it stamped on the outside of the tank or on a sticker somewhere on the car ?