See where the "reticle subtension (")" is? That variable would then become 3.6", and if somebody had a mil-dot reticle and looked at the same tgt. at 830 yds. right next to this guy who's using the Nightforce NP-R1, here's what it would "gap" in his reticle--

27x100/3.6/x=830

x=0.9 mil.

Now if i were looking at that tgt. with my Nikon Buckmasters mil-dot at 18x (now 2.4 inch per hundred yds. between dots) instead of the mil-cald. power of 12 here's what it would gap in that reticle--

27x100/2.4/x=830, x=1.35 mils--

ONE of the nice things about understanding how to manipulate this formula is that if u have a mil-dot reticle that's cald. for a power that's lower than the highest (mine above), u can "mil" at a higher magnification which allows u to define the edges of the tgt. better--most of the time.