If you logged in with your old account, and did not have to re-create it, this would be a problem with the BB undergoing a major version upgrade.

Some new data tables were added and numbers recalculated. I think several people may have lost some posts counts.
The difference is Senior members have about 100 posts, unless that changed too, I'll have to go look at the triggers for labels.
Personally I'd love to do away with the post count. Just because someone posts a lot doesn't mean they are senior.. But it's the best game in town. All other rankings have separate issues.