Don't get hung up on Hub score. It has no bearing to the profitability or traffic of a hub. It's just a general guide of potential quality. For instance, a hub score of 45 or less is usually a good indicator that the hub is short and without substance. But a hub score of 75 might not mean its better than a hub scored 95. As long as your score is over 60 on an individual hub, I wouldn't worry about it.