@ratimov, it's dependent on their first post in the 14 days.
unless an actual recount (that Theymos does manually run sometimes) changes your post count or activity - this is probably quite rare though.
- Activity points will be recounted after each 14 days. It is only true for members who always reach the cap of 14 activities within each 14 days
Actually, I think there's an internal rule after 300 activity and posts that your activity goes up by 14 after your first post.