The SV fuel calibration can be manually edited. That will save you the hassle of redoing the calibration.
Export the files to your USB key from the setup menu. Look for the file with EMS in the name and open it with a txt editor. Look for the calibration sections. Search for "user_cal={". The format should be obvious:
user_cal={
valid=1
name=MAIN LEVEL ; NB this is the name I gave it
num_points=11 ; this should match the number of points following
point={
volts=0.00114441
value=0
}
The "volts=" is the voltage reading, value=" is the value in litres.
Hint: If you go back to the fuel calibration in SV it will allow you to edit it there also but I'm not sure if you can remove points. What is nice about the calibration is that it shows you the voltage of the current level of your tank. If you have to redo just one level, fill it to that point, read the voltage and manually edit the file. In your case, you want to know what the voltage is with the tank full and edit that volt/value pair. You may have to edit all the volt/value pairs as they are all out ten litres.