PSO-1 QUESTION

I have notice that some PSO-1 4x24 scopes turret knobs are graduated 1-10 and some are graduated 1-20. Whats the dif. Is there a different model number for each style?

or is one model graduated 0-7 and the other 0-20?

Follow this link it will give you the lowdown. Rick
http://www.kalinkaoptics.com/Manuals/KOPOSPFixedManual.pdf