It is comparing foot size to the size of a barge. Everyone knows that a barge is approximately 700 feet long. Put the hyperbole in a different color so that it is obvious to your teacher. Hyperbole is a figure of speech which is an exaggeration. Such statements are not literally true, but people make them to sound impressive or to emphasize something, such as a feeling, effort, or reaction.
Hyperboles are common in everyday language and in poetry.