At McDonald's, an order of small fries and a small soda contains 420 fewer calories than a large order of those same two items.
The purpose of this particular "numbers game" was to show that no matter where you eat, you always have the ability to make better choices.
Many times, when people go to fast food restaurants (especially if it's by choice), they resign themselves to large portions and high calorie amounts, thinking "hey, it's not supposed to be healthy."
Similarly, a lot of people balk at the idea of calorie information being posted at fast food restaurants, claiming people don't go to a burger and fries joint to eat healthy.
Perhaps, but that doesn't mean these customers aren't interested in knowing how they can integrate a food they enjoy into a healthier way of eating.
The example provided in this answer is proof that a craving for fries and a soda doesn't necessarily have to add 810 calories to your day (large fries clock in at 500 calories, while a large soda contributes 310 calories.)