So the claim is that there have been at least 9 million hours played per day by an unknown number of "kids". That's... profoundly difficult to unpack from "more

So the claim is that there have been at least 9 million hours played per day by an unknown number of "kids". That's... profoundly difficult to unpack from "more than a millennium per day". And I'm still not actually sure that's what they meant. Is this kind of construction common? I understand "man-hours", but I've never heard words like "millennium" inserted like that.