Not unlike the evolved meaning of 420; this began, locally, when a manager (at an undisclosed business) always performed his morning ritual at exactly 8:15 in the morning. Everyone in the company; and, by extension, ex-employees; began describing their potty time as "815" (pronounced Eight Fifteen).
This number is the flight number of the plane along with many other things linked with the island and its characters.
815 has become a number universaly known as mysteriously spooky and beyond coincedence.
It is said 'eight fifteen' not 'eight hundred and fifteen', by the way.
'urr i dunno....about 2.47? Ill go and check'
'dude, it IS 2.47, exactly'
'Talk about 815!'