I agree with your skepticism here. However, it's possible there are 240k active writers, if only an eight, 30k) earn over $10 and if Medium doesn't include in their calculations writers earning under $10 a month.

If this is so, then you'd have to reduce your estimates regarding the median earnings, because 88% of writers would be earning under $10k, and part of Medium's payouts would go to them. Unless you already included this?