Only 'fifteen' (of them) showed up on time.
Their boat finished 'fifteenth'.
one 'fifteenth' of the total
(..) Bobby's got it. Bobby's got it. Good night. Good night, sweetheart. I do love you, but... I'll meet you in fifteen... I'll meet you in fifteen minutes. God, why did I say that? Fifteen minutes? What the hell's wrong with you? (..)1992 Twin Peaks: Fire Walk with Me