I recently got my first fly plaid. It came with the corner pleated and the pleat sewn in. A loop is sewn on the under side of the pleat. What does the loop go around?

It doesn't fit around the top button of the Prince Charlie, too far down.

It doesn't seem to fit on the button on the epaulet, too far up. In fact the bottom corner of the fly plaid drags the ground.

Does one sew a button on the left front of the PC for the loop to go around?