Fuel gauge shows not full but filled up?

Run the gas in to the SECOND click.

Then, don't worry about it.

The important point is that you don't run out without a warning.
Whether or not it shows F when it's full is inconsequential.......especially if you are paying for the repairs.

P.S You might want to update your profile to show that model and year of car that you currently have.

 

don't forget, there are 2 gallons left when it reads zero dte, safety fuel, so you're missing around a gallon?

 

For the 1 bar missing issue, do as others suggest and fill to at least the second click. Mine sometimes quits early, sometimes way early. My Subaru doesn't stop early, but it has somehow reached states where the gauge stops 1 to 3 bars short of the top. It always returns to normal on the next refill.

For the '0 miles left', remember that the gauge is nonlinear, the bars don't necessarily represent the same amount fuel, the top of the gauge isn't at the real top of the tank, and the bottom of the gauge is not at the real bottom of the tank. All this comes from past cheap gauge components, and the necessity of managing customer expectations. Customers get hot when get stranded without fuel while the gauge is still above 'E', or when changing condition cause the tank runs dry faster than expected earlier in the journey. Thus, the manufacturers typically built in a lot of safety margin at the bottom, so customers can't legitimately claim 'But the car said I had enough gas! It didn't warn me!' Sorry, but you had plenty of warning and cannot blame anyone else.

If you want to be really safe, then you must just put up the car's warnings to GET GAS NOW! when it take only 8.5-9 gallons. If you want to operate down into the last gallons, shaving the safety margin, read this thread first: [WARNING] Running out of gas (Gen III) | PriusChat

Here are other reasons why large safety margins are needed: