I doubt anyone can give you reliable answers without knowing how the stick was calibrated and for what tanks. They were not all the same.
The best way to calibrate to the stick is next time you refuel, stick a tank, mark fuel level, then put in 20 or 30 gallons and restick the tank, mark the stick. From that, you can calibrate to the markings.
Then do the other tank same way. You can mark one side of the stick for Port and the other for Stbd. If you have 3 or 4 tanks, you can use the sides of the stick to calibrate.
I suggest you then fill the tanks and restick the tanks and mark for Full for that tank.
The bottoms of the tanks are probably sloped so, at some point, the calibrations won't work as accurately.