Chloe, I have read numerous articles about the confusion around seemingly getting paid less for one article that would appear to have lower numbers than another.
This is a complicated algorithm, but I know this much about math:
To keep things really simple let’s pretend that in the month of January a thousand stories were published on Medium. Only 100 were for members. Next month the same amount were published, but there were 250 stories from members. That right there shows you the difference in the divisor for spreading out the funds to pay for member only articles.