Man you made me go out to the garage and double check myself. It's just the instant bar graph at the bottom of the display.
On another note, I just killed my mileage checking and never turned the car on! I've got 80.6 MPG on this tank so far (only gone 11 miles) but when I cycled though the Trip A/B / odometer it reset it back down to 79.8!
Hope you enjoy the car and when you have more questions shoot away. This is a great freindly forum who are, for the most part, very helpful.
AL