Functionality of unread posts button

[#1]

I just did something unusual for me I clicked on the link from the latest newsletter (arrived by email) to the blog posting then closed the browser. I then used my usual link to the forum and clicked on "unread posts" - there was only one.
It appears that last visit is interpreted as visit to the community site not visit to the forum section.
Is it worth changing this so that only a visit to the forum section triggers it.

[#2]

The unread post is only those in the current browser session, to see unread posts from previous sessions you have to click on the other link next (read all unread posts)

[#3]

I know that  - the question is "why?" if I haven't been onto the forum part of the site

[#4]

Dont know Jim, never done it that way round, next time maybe.  I do occasionally find unread post for some reason unknown to me