When the split of the forums was implemented, one of the adminstrators volunteered to move "recent" posts from the tech side to the community side to get things started. (To "populate it" as we called it. It was kind of like when you stock a pond to get it started.)
There wasn't a "carved in stone" date of what "recent" meant--we left it up to that person's usual sense of good judgement--as we did with which original posts were moved. After that, a few of the posts were moved back to the tech side, and a couple more tech posts may have been moved to the community side, IIRC.
We really weren't worried at that time on making sure it was "accurate"--we just wanted to get it started. As a result, trying to compare the two going by the total numbers is somewhat of a waste of time. However, if you
really need to do so, and why that is might be a mystery to many of us
, you should probably pick a random date after the forums split, and count from there. And still, you'd have to decide whether or not to include older threads with newer posts, etc. And even then, I don't know if it reflects much of anything--but if it makes you happy, goferit.
EDIT: Well, I guess in the time it took me to type, Paddy got it answered. (And I even tried to protect her identity in this post.)