Re: Not very reassuring, is it
It's not bogus, it's just math.
I'm not a mathematician (or statistician) but my job does involve a large amount of working with statistics. In a layman's-terms nutshell:
Say you have a big bag of things -- marbles or whatever. Doesn't matter what they are, what matters is that each one is individual -- unique -- and your job is to record them. You don't know how many are in the bag to start with, and because your boss is a jerk, you're only allowed to reach into the bag, grab one at random, record it, and put it back afterwards, and then start the process over again.
So you've been at this for a while, and at first every one you grabbed was new. Then over time, you started seeing ones that you'd already recorded. Eventually, you reach a point where nine out of ten times you reach into the bag, you're finding one you've already seen.
At that point you're pretty safe to say that you've seen 90% of the marbles in that bag, and you can even make a decent estimate about how many there are, even though you haven't counted them all yet.