Fuel fillings not matching up

Hello, im having a bit of a headache with this topic.
I have a unit with **** TD-150 sensors in an Analog conection to the gps, the truck only has one tank and the capacity is 378L. when we first installed and callibrate the tank, the callibration table came out wrong because our transfer pump and meter were not working propertly, we fixed it and made the calibration again, we made it by adding 20L. until the tank was full.

The thing is we used to have 89-88 percent of accuracy before the recalibration, and now that we recalibrated the tank we have a 93-95 percent accuracy to what acording to our client is what they fill with fuel the tank, my question here is, is there a way on Wialon platform that i can get a way more accurate reading?? what parameter can i change so that the reading is more precise.

Thank you, any help is appreciated