supermarket butter

Can anyone help me in calculating the butter fat percentage in commercial butter offered in supermarkets.  I am looking for an unsalted butter with a high percentage of butterfat - a dry butter.  I checked the facts on the backs of several different supermarket butters and came up with a total fat content of 11gm and a total weight of 14gm in a tablespoon of butter.  If my math (always questionable) is correct that's only 78% fat.  I also thought that in the US butter was required to have 80% BF.  Any help with this would be appreciated.