The Fat is not the only indicator for the Quality of Butter, but it's important-the amount of
Butterfat in the finished product is the Key. In the USA, all products sold as Butter must contain a minimum of 80% Butterfat. In Europe Butter generally have a higher content like up to 85% Butterfat. (As far as I know, correct me if I'm wrong)
It's on you to decide if it's good or not. Smell it, taste it.... The best Butter for me is the one I know from Germany, fresh and traditionally selfmade Butter from a Farm.
The more Fat, the better it is.
Butter 
