When are points allocated for "read an article"

I am not sure how this is supposed to work. I saw that no one on my site so far has recieved any points for the rule "Read Article" so I tested by going to an article on my website whilst logged in and I stayed on that page for around 15 minutes (and also made sure I scrolled all the way down to the end), yet when I check my points history I don't see the points being awarded.