sometimes a hub may have a hard time reaching 500 words. From my research on how to write hubs that get read. What I found over and over is this. A hub or article should be between 500 and 600 words. This will make it long enough to be informative and entertaining ,But not too long . People on-line are looking for info or entertainment, and do not want to spend the time reading something to long.
I think a hub is judged on content, and number of words would only be looked at if the hub had nothing of value ,or is nothing but an affiliate ad. If I am wrong please let me know.