I had my rear tires filled by the dealership when the tractor was delivered about 5 years ago, and never gave a thought as to how much they filled the tires. Today when I was filling the tractor with fuel I guess the outside temperature and moisture were just right, and I could see a line on the tires exactly where the RimGuard was installed. It is about an inch above the midpoint in the rim. When I asked about the quantity that they installed, I was told that it would be about 3/4 of the tire's diameter. What is the correct amount of fill that should be in the tires?