"first new post" button

When I click the button next to the thread title that says "first new post" on the mouse-over, it seems to be taking me to the last post in the thread. In most other forums Vbulletin is set so this button takes the user to the first post in the thread that is unread by that individual user.

It appears that something was changed mid-morning, it is now taking me to the first unread post in the thread.

Thanks