I don't have the Dynon manual but assume it is very similar to the Advanced Flight Systems that I have - clip below. I set mine using just the fuel truck fill gallons and the fuel used readings off the scree. I did it three times getting closer each time. Hope you get it worked out.
Version 15.1 AF-5000 Series Install Manual 161
Fuel Flow Calibration
The accuracy of the fuel computer is affected by the value of Counts per .01 gals (K Factor). The Counts per .01 gals (K Factor) sets the calibration of the instrument to match the flow transducer and the variations in the installation. After running a tank of fuel use the following formula to adjust the accuracy.
The Counts per .01 gals (K Factor) is adjusted from the Fuel Flow/Computer page in Instrument Calibration.
New Counts per .01 gals = (Old Counts per .01 gals) x (Disp GAL USED/PUMP GALS)
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