Was September an unusually good month for X1 sales, then? If I could see the data from the previous four months, plus #'s of weeks used to calculate each, I could come up with a better baseline than September. I'm not compulsive enough to keep track of those numbers myself, though (almost, but not quite).
It was pretty good. Nowhere as good as the juggernaut that is the PS4 though. X1 sales weren't that good in the summer, they had no exclusive games released.
538k for PS4, 284k for X1.