science2 is my largest subreddit. It has over 2,500 subscribers.

When I look at the traffic stats the uniques per month almost never go over 100. Does this mean, on average, 2,400 users have subscribed and then never accessed the subreddit again? Also, what counts as a unique? If someone clicks through to a website from a link being fed to their homepage does that get "credited" to the subreddit? Or is it only counted as a unique if someone goes to the comments page?

I'm guessing what happens is that people subscribe but forget and then the links in science2 never get enough upvotes to make their homepage list. So as a practical matter the fact that they are subscribed is irrelevant because they never see the posted links.