Based on the food guide, it goes back to recommended serving size. What are you going to eat in one sitting? Because of the size of the crackers--a thinner cracker versus a denser cracker--you would tend to eat nine of those and four of the other. That's the example.
I'm not going to dispute that it's confusing, but I'm saying there's a rationale as to why it's structured that way. You're dealing with different densities, sizes, and types of products.