The earnings are strictly dependent on the audience profile(location, age, gender etc.) and the theme of the channel as the earnings are essentially a cut from the ad view and click costs.

I've watched some videos from similarly sized youtubers disclosing their earnings and socialblade seem to be quite off the mark most of the time probably because they don't have a good way to estimate the profile of the audience accurately enough.

Rule of the thumb is, a finance channel with American audience makes 10x-50x more per view than a Bangladeshi channel about gaming.

So it's not easy to guestimate.

I think SocialBlade just gives a range since RPMs vary wildly due to a ton of factors (e.g. geography, niche).

I'd guess Asian viewers in the history/tech niche have lower RPMs compared to something like American viewers in the finance niche.

$821 to $13,100 per month is a very wide range. The amount he actually does makes falls within that range but it would be hard not to.