Learning to understand what all the numbers mean on a food label, the different nutrient parts, such as fat, saturated fat, sodium, etc, and ingredients, can be confusing. Calories, of course, are a big part of the nutrition label and, probably, is a number where most people stop. If it has less than a certain number of calories per serving that is how they decide between one box of cereal, or crackers, or chips, and the next.