For one patron of one of Manhattan’s many Pret A Manger sandwich shops, a few inches of empty space in the packaging for the chain’s wraps may be worth millions.

On Monday, the disappointed diner, Yee Ting Lau, filed a class action suit in the Southern District against the chain over the amount of space between the two halves of a wrap she purchased in June and joined a growing list of plaintiffs seeking damages for the air content, or “slack fill,” in their food packaging.