It would be reasonnable to build the simulated universe as similar as possible to the outer universe. Even if that was the case we still could not tell the dif

It would be reasonnable to build the simulated universe as similar as possible to the outer universe. Even if that was the case we still could not tell the difference between a real universe and a simulated universe. We look at our universe and observe X, then what? Are we in a simulated universe and in the real universe something slightly different X' is true? Or is X simply true in the real universe in which we live? [And in a galaxy far away some aliens are running simulated universes in which something slightly different X' is true and observed by the simulated aliens?]