It's hubpages rating for your hub, referred to as a hub-score. The higher it is the better. Things that will effect the score is how many people rate it up, how many people comment on it and interaction is on it, how many views, how long people spend on it, when they do read it, that it meets the requirements, it's original, etc. So the fact that it went from 60 to 62 is a good thing. Much of the scoring is a mystery though. Some days a hub might have a hub-score of 77 then a couple days it will be 70, then back up to 77 a week later. It changes a lot, and don't get too depressed if the number goes down, because chances are it will go right back up.