96-4 is ground round, the leanest you can buy.
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The more I read on this, the less I realize I know...
However, as long as ground round has at a minimum of 70% lean and maximum 30% fat and comes from the round, then it is correctly labeled. It could also have 90% lean and 10% fat and still be labeled as ground round.
http://meat.tamu.edu/ground-beef-labeling/