Population Question?

Stingray

I collect 67s and just purchased a PSA 9 #261 with a population of 24, I also have #259 in PSA 9 and that one has a population of 94, how do to cards only two numbers apart have such a difference in population? Are there some double prints in 67s, I know there are some single prints in series 7.

Stingray

Glynparson

alot of it is where the card was located on the uncut sheets.