^ The article I cited was specifically talking about sign-ups FOLLOWING the airing of The Vulcan Hello on CBS broadcast TV.
Where do you see that? From my read, they broke the record after the airing, but that doesn't mean they're not counting the signups from throughout the day.
Frankly, I'm guessing the wording is sloppy, and that "Following the" isn't really meant to indicate when the record was broken. I'd be surprised if it didn't break the record even before the ep aired.