From Lostpedia:

The Numbers: 4 8 15 16 23 42 are a major recurring theme in Lost. They appear in the Valenzetti Equation and in the lives of several of the characters. The Numbers, as revealed in The Substitute are related to individual people. Written inside the Cliffside cave, many names appear with numbers beside them. They all are crossed out except for the six Candidates, with 4-John Locke, 8-Hugo "Hurley" Reyes, 15-James "Sawyer" Ford, 16- Sayid Jarrah, 23-Jack Shephard, and 42-Kwon, revealing that the numbers represented the candidates the entire time.

But won't we all feel silly if no one plays those numbers and they are the winners tonight?