Eight copies moved was enough to propel me to #81 on the Fiction>Action Adventure>Fantasy (Free) category. That tells me that is a very low traffic category. So, writing to that genre is either very good, as it is underserved, or very poor, as shoppers don't use that category. I'll go with option #2.
Eleven copies put it at #9000 in the free store and pushes it up to #60 in Action Adventure>Fantasy (Free).