Notwithstanding horse snot, the simple point was that if you mix brands, or series of hones, the progression may not represent what you might think it is. Due to the different rating systems, and differences in performance, a progression up just grit numbers may not actually be an upward progression. The result is that a seemingly higher grit hone actually can be more coarse than the preceding hone even if it has a higher number stamped on it.