Hmmm J160, Russ must be the model with round fuel gauges and not the glass sight window.
I have the round fuel gauges, and they never seem correct, I have made dip sticks, to measure the wing tanks to be sure.
My J160 is flown with two large chaps (90 + 110kg), gets close to MTOW, so the fuel level needs to be accurate to keep under MTOW.
Filling both tanks and two average people will put the J160 over the MTOW.