Sweet, did eventually find it isthe book staring at me from the top of the page.
Will do 2 fills easy. Tank is empty now, so today will be the first fill. Gotta do a few tip runs around tomorrow, then ave to drive to Brisbane airport and back on Saturday.
Book says, fill with 1/4 to go and that should calibrate it. So really only needs 2 fills not 2 tanks.