When dealing with sight systems, there is exactly one distance that has only a single zero. In archery, this is called your "High Pin". Every other distance will have two zeros. The distance of your High Pin depends on the sight geometry and the velocity of the projectile. When you try set a pin closer than your High Pin distance, it screws up the spacing relationship to all your other pin distances, making your pin gaps appear all wonky. I wouldn't think that the concept of High Pin changes when an airgun sight system is involved.
If the clicks you're seeing between a 10yard zero and a 30yard zero end up being different, it's probably because your 10yard zero is closer than your airgun sight system "High Pin" distance. Which really makes it a zero for a much further distance.
If you look at the reticle display in the other Strelok thread, you'll see how this might work. Reading the left side of the reticle look for 10 yards. On the right side of reticle you'll see the "real" sight in distance. Somewhere between 75 and 82 yards.