Question Regarding Fuel Gauge Calibration

I already know the procedure to recalibrate the fuel gauge, so that is not my question.
My question is whether or not the fuel tank must be full in order for the calibration to work properly? It makes sense to me to think that it would, because the current fullness of the tank would set the standard for what the gauge considers to be "full", correct?

Anyone knowledgeable of this subject please respond. Thank you.