The sum of 4, 8, 15, 16, 23, and 42 is 108: the number of minutes on the timer in the hatch. 108 times 5 is 540, the number of days Dr. Candle indicates in the orientation film that a team will live in the Swan station.
The title card at the beginning of the orientation film Jack and Locke watch has a higher pitched version of one of the main themes used in the shows music by Michael Giacchino.