there are two main table types:
1. the fuel volume vs. sender input (note, i accidently labelled this axis wrong it seems as %). This table tells the PCM how many liters/gallons of fuel you have remaining based on the input in "AD counts" from the fuel sender. IN vehciles where the cluster communicates with the PCM via the class2 bus this table also specifies the gauge calibration. In later vehicles there are actually 4 tables for this.
2. the other table is the fuel gauge output PWM control, for gauges that are directly wired to the PCM (ie. not class2). Changing this table will affect the signal sent to the gauge based on the % remaining fuel, ie. the fuel volume divided by the fuel tank size.
The calibration of these things depends on the relationship between the sender output and how much fuel is in your tank, this depends on the shape of the tank and the response of the sender. This is why the curve is a little funky cos rarely a fuel tank is a nice square or rectangle shape.
You can log "Fuel Tank Level Sensor (V,V)" which is the sensor voltage ( multiply by 51 to convert to AD counts). Also the "Fuel Tank Level" which is the volume of fuel in the tank from this table.
The % remaining is then a simple divison by the capacity.
Chris...