New Posts?

So, I'm everyone knows the New Posts line on the homepage? Well, right now mine says:

New Posts: 0

Even though there are plenty of threads in the forums that I haven't actually read yet, several of which are even in the Recent Threads list. What is the New Posts number based on, and is there any way to reflect it to make it show the actual amount of new posts that I haven't read?

Number of posts since you've last signed in.

So if I had 100 new posts, I signed out, and signed back in right away, the number would be 0? Which is strange, because I never sign in, my computer somehow automatically signs in so as soon as I type speedsolving.com into my browser, I see "Welcome, byu" in the upper right.

Auto-login. The site knows whenever you come on. It would be a pain to have to log in every time.