What this is really saying, this part right here, 60 factorial divided by 60 minus 4 factorial, that's just 60 times 59 times 58 times 57. That's what this expression right here is. And if you think about it, the first number you pick, there's one of 60 numbers, that number is kind of out of the game, then you can pick from one of 59, then from one of 58, then of one of 57. So if you cared about order, this is the number of permutations you could pick four items out of 60 without replacing them. Now, this is when you cared about order, but you're kind of over-counting because it's counting different permutations that are essentially the same combination, the same set of four numbers, and that's why we're dividing by 4 factorial here. Because 4 factorial is essentially the number of ways that four numbers can be arranged in four places. The first number can be in one of four slots, the second in one of three, then two, then one.