Right? Well it's a nice argument, but it requires just a bit more care. What they've given me is two procedures for a 6-train, one that starts with a 5 train, and the other that starts with a 4-train. For this to actually give an exact count of the 6- trains you really have to check first that you get all of the 6- trains in one of these two ways, and secondly, that you haven't counted any 6-train twice, that is, that you can't get the same 6- train coming out of both routes.