it looks off center but its not, have a look at the front bottom of the front sight, there will be two little nicks in the metal and they should line up, i would imgine that is some factory easy sight way, its on the front sight of the mosin i have as well.. there is a full back setting on the slide yardage thing and it moves with spring tension and is default to three, then you move it forward so its on the 1 if your shooting 100 and 2 if 200 and so fourth. I think they set the sights at the factory, take a close look and you'll see what i mean
mine looked off center as well till i examined more closely