84 is a good hubscore. Really anything 70+ seems good, though sometimes there are great hubs in the 50-60 range.
How to raise your hub score? Make sure you have good content, a nice layout with pictures, don't break any rules. Be social with other hubbers as they *may* visit your hubs and rate them (up or down so make sure they're worthy of an up). Being social includes [properly and sincerely] commenting on other people's hubs, and being helpful in the forums.
Getting traffic may also help. Just search "traffic" up above to find lots of hubs about traffic.