Dean..
The post count disparity, I think, resulted from restoring an older member file during a forum software problem's repair.
Some older post count numbers went to that great bit-bucket in the sky... the actual posts were not lost, just the counter got changed for some members.... get crackin' and catch up!
The "Member" and "Senior Member" you see is an automatic default setting for the Custom User Text portion of your Profile.
I think the title changes to "Senior Member" at 200 posts, or close to that.
Also, at some point (maybe 100 or 200 posts), the ability for you to change the title to anything you like becomes available in your Profile settings... hence some of the witty titles you may see.