I'm sure you'll figure out the calibration but here's a tip if you're putting in a new sending unit.
I have seen some bad floats RIGHT OUT OF THE box so before you install it and put the tank up and fill it etc....
1st, take the float and submerge it in water and look for bubbles
Bubbles are bad! It means the float has a hole in it and will sink even when the tank is full. It will always read empty and you'll drive yourself nuts debugging everything else because you KNOW you just put a new sender in.
Does it sound like I'm speaking from experience?
This info comes at the expense of a long bad day for me....
I'd hate to see anyone have to do this twice as it just isn't fun!
Good luck!
Rudy