As filmmakers, we can slip in all kinds of little jokes here and there. This one comes right after a brief discussion between two characters about a girl. Character A insisted that B likes the girl because of the length of her skirts.
"They're not that short," Character B protests.
The next scene includes this shot of a different girl:
It has no bearing on the story whatsoever as the waitress is a background character. But the wardrobe is absolutely intentional to play the gag a bit longer. These moments aren't just for the humor. These choices help reinforce key ideas and are a great way to practice visual storytelling.
Your Media Production Mentor