Any reason why you didn't go with the 7.62x39/300BLK reticle option that specifically has a subsonic 300BLK BDC in it?
Anyway, as it turns out, Strelok says if you sight in two inches low low at 100 yards, it's surprisingly really freaking good. Top of the BDC post is 111 yards, the 125 yard hash becomes 130 yards, 150 yard hash is 152 yards, the 175 yard hash becomes 176 yards, and the 200 yard is dead on.
Those are really close, so if you use it as intended you are going to generally be hitting just a skosh high at every BDC range, probably within the margin of error of your shooting unless you are running an amazing precision rifle in .300BLK subsonics. LOL
I'm actually shocked at how well this works out. I had no idea the trajectories were that similar.
FYI for the simulation I used a barrel with a 1:7 twist rate and the ammo was Federal American Eagle 220gr, part number AE300BLKSUP2, at a velocity of 1000 FPS which is what they rate the velocity at right out of the box. You might get very slightly different results with a 16" barrel vs. an 8" barrel or something, but .300BLK subs aren't really that sensitive to barrel length changes, so honestly I think you're pretty good to go regardless.