A hub score is the score on each of your hubs. This score normally fluctuates up and down on a daily basis.
When you first create a new hub, that hub's score will be really low but it will slowly increase. After that, it might still decrease but it shouldn't decrease that much anymore.
Some factors used to compute hub score is the quality of the hub as measured by the quality assessment process, the length of the hub and your hubber score. To find out more, you can check out the learning center guide on hub scores. Here's the link: https://hubpageshelp.com/content/Learning-Center-h... .