Oddity

I filled up my 03 today right before work. This is one of the warmest fillups I've had with this car at 73 degrees. The computer stated 53.4 mpg. When I calculated the numbers to get what the actual fuel mileage was, it came up exactly even at 53.4. As usual, I filled up the tank to the top of the filler tube. Normally my computer is optimistic by about 10%. I'm curious to see what the next tank will show.