I had seen that, too when underneath my C at an oil change. I guess it could be a left and right side fuel pick up since the tank is so oddly shapen, which would make sense. Also the display on that screen shows a symbol that never changes and that is 19g. 19 gallons is the capacity of the tank.
BUT, what I don't understand it the moving numbers in the L and R columns...They don't ever seem to equal anything less or more than one hundred. If it was a fuel totalizer, the numbers from both columns would decrease over driving time. Maybe they do and I'm not paying close enough attention. I AM trying to drive and look at the same time.
Next time I go to the DLR I plan to get to the bottom of this. I'll let you know if nobody figures it out befor that.