When we talk about calories in cereal, we talk about the amount in a bowl, not the amount in the whole box. When we talk about calories in milk, we talk about t

When we talk about calories in cereal, we talk about the amount in a bowl, not the amount in the whole box. When we talk about calories in milk, we talk about the amount in a glass, not the amount in the whole jug. So why are we talking about how many calories are in the whole tub of ice cream?