Explaining the numbers is kind of complicated. Suffice it to say, each number represented one of the main characters who were under consideration for the position of Protector of the island. Since the island has special, unique properties, it’s been sort of a holy grail; it needs protecting from exploiters. The current protector, Jacob, knows that someday his time will come to an end, so he is on the lookout for his successor. He builds a device that allows him to observe from afar; each number is a setting on the device’s dial: Jacob can set the dial at 8, for example, and watch Hugo Reyes. Through these observations, Jacob chooses a group of people who he thinks would make good successors, and he brings them to the island. Eventually out of this group of candidates, one emerges as the next protector.
There’s a lot more to it than that, but I think that what would be more useful to Once fans is to know the basic tenants of Lost, which include
*you always have a choice
*take responsibility for your own actions, but learn to forgive yourself and others
*balance science with faith
*communicate with each other
*rules may seem arbitrary, but we need them to live peaceably
*live together or die alone