Me not smart but sometimes me hit self on head with club and make brain work. Me try now.

bonk

One particular realization of the AdS/CFT correspondence states that M-theory on the product space AdS7×S4 is equivalent to the so-called (2,0)-theory on the six-dimensional boundary. Here "(2,0)" refers to the particular type of supersymmetry that appears in the theory. In this example, the spacetime of the gravitational theory is effectively seven-dimensional (hence the notation AdS7), and there are four additional "compact" dimensions (encoded by the S4 factor). In the real world, spacetime is four-dimensional, at least macroscopically, so this version of the correspondence does not provide a realistic model of gravity. Likewise, the dual theory is not a viable model of any real-world system since it describes a world with six spacetime dimensions.