Thread: New Posts Button

I have in recent times begun to use the New Posts menu item when visiting the forum. When I use it there are thirteen pages of posts of which six appear to be accessible. Is there any way to mark all posts read or how do I reduce this to just the posts since my last visit. I opened all the pages up to six and then shut it down and re-opened it and the same pages appeared with no change. In short how do I get this to reflect just the new posts since last visit please. Thanks.