Because the right front cell doesn't have a quantity probe, the reading from the left cell is doubled. So, if there is some problem getting fuel out of the left cell, you can get a false "high" reading for the fuel still in the front, even if the right cell is nearly empty. A vague memory is tickling the back of my brain about this, but it was 30 years ago and turned out to be just something that I had to tell the maintenance people about before it became a problem.