The "tables" are just an artifact of the random number generator. The game picks a seed number for the generator, which determines what numbers come out of it, which determines what sort of charms you'll wind up with. For "toy" randomness like in video games it's not unusual to just pick the time of day. But MH3U's mistake was to attach that seed value to a hunter forever which turned into a huge pain for people looking for specific charms.A total pain in the ass. New charm tables are decided every time you load, which is better, but I'm not really sure why they even need different tables at all.