"Lima" Count
I'd also like to add that there is a counting system that is even more efficient than the U-APC. It's called the Lima count, credited to John May. The P.E. is a whopping 88% but includes a drawback that the Betting Efficiency is only 65%. Betting is more important, that's why Hi/Lo or K-O dominates in that region.
A couple of corrections. First, the PE and BC are reversed. It is impossible to have a PE much higher than 70% with a single count. Also, this count was discovered years before John May called it "Lima" in his book, by myself and others. I've made dozens of posts about the 3-7 vs. 10 count since 1997, and Pete Moss actually used his own version in casino play.