I see that you have 4 followers without a single hub and that is why you have the score around 50 (otherwise it would be lower). I guess this means your followers are waiting to read your hubs so start writing. Great content, quality hubs, page rank on Google, backlinks, traffic, your hubtivitiy (asking and answering questions, participating in forums, commenting etc.) - it all affects one's hubscore. People who reached a 100 in their hubscore usually have more than a hundred hubs and a lot of traffic driven to these hubs. I have to add, it doesn't really matter that you reach the maximum hubscore. There are many, many great hubbers here on hubpages whose score is between 90 and 100, but their hubs are better than of those with a higher score (it is relative). And the last, but not less important, you just need to keep your hubscore above 75 because it means there are enough page hits to make your articles interesting to read. Remember that hubscore is usually not static and the rise and fall in numbers depends on publishing new hubs and hubber's hubtivity.