Actually, if you study the maintenance booklet, there is an identical sized square hole in the cover. As the maintenance services are completed, a "coupon" is removed from the pages when the service is completed. This uncovers the "next" coupon, with the next mileage showing through the hole in the cover. Just put the booklet in it's place in the door panel, and the mileage for the next service interval can be seen, even with the booklet closed, due to the hole in the cover......Gilly