Martin, setting this table up is actually one of the simplest tasks you will have as a mapper as it can be so easily simulated.

Run the ecu off an external variable voltage power supply.
Set the 13v point to 0.5 first as good starting point

Then record the AFR at idle.

Set the voltage to 12V and alter the compensation value until you have the same AFR again, then 11V etc

It needs doing on a per injector configuration basis, so it will only need to change if you change the injectors for another type or alter the fuel pressure.

It doesnt actually matter if when you do it the AFR is correct at the time or not, so you can do it before youve finished the rest of the mapping of the car, so its good one to get setup early on in the mapping process as it stops you getting spurious results during mapping.