The hubber score is a combination of the hub scores average, and your participation in the community. Asking and answering questions, participating in the forums, reading and commenting on hubs, and hubhopping. Don't worry about it unless it drops drastically. Then you might try participating a little more.
The hubscore is a combination of the quality of the hub, the comments made, and how many views you have. As a hub has been out for a bit, it will start to lose views. The hubscore will then drop. If you just go in and edit it a little, the hubscore will go up and you might get a few new views on it. That will help keep the hubscore up and keep it from going to unfeatured. This one, you want to keep from dropping too low. If it gets too low, it will not be eligible for the search engines and could get unfeatured. It also does not pay when it gets too low.
Hope this helps you.