The comparison is there. I don't know what else to say, to be honest. It's based on comparable servings of food. You would eat a bowl of cereal versus a bowl of cereal. It might be denser, thicker oat granola type of cereal versus a flake cereal. It might be bigger crackers and smaller crackers.
The premise of the comparison at the top there is to compare two products in the same category. What would you eat of product A in a sitting, as opposed to what you would eat of product B in a sitting?