There are two factors going on with an unpublished hub. One is that the quality of what is written in the text and the uniqueness of your title according to Google bots will affect how high the score is. That aspect is easy to follow.
However, unpublished hubs will automatically go up and down over time, and it is unclear why this happens. There seems to be some mechanism which randomly does this. Once a hub is published, how well it does in traffic will affect the hub score and nothing is random anymore.
Do not worry about the score of your unpublished hubs until you are ready to publish them. They should have a score of at least 45 before you publish them.