I found something but it might be long to read through, dated from..Feb last year. Might be helpful...
https://chartmasters.org/2020/…x-albums-and-songs-sales/
Tltr. It basically says the the estimated 50 million doesn't just encompass physical & digital sales but also other things.
So it's not pure sales (digital and physical copies) alone.
But again I don't know this person, so i don't know their legitimacy with sales and what not.
Hopefully it's helpful.