Paula has a jug with 3 2/3 cups of milk. She pours 2 1/2 cups into a thermos. What does the distance between 3 2/3 and 2 1/2 on a number line represent?

the amount of milk left in the jug
the amount of milk in the jug and in the thermos
how much more is in the jug than in the cups
the amount of milk that filled the jug