It's not $2.2 billion, though. First off their own $3.7 billion is wrong because that's more than 4%, the actual number should be closer to $3.2 billion - $3.24 billion (I've seen $80 billion floating around). So the actual article screwed up their percentages somewhere when writing it out. The market would've needed to generate $92.5 billion in revenue to get $3.7 billion in GP-style sub services as 4%, not $80 billion or $81 billion.
60% of that $3.2 - $3.24 billion is $1.92 billion - $1.94 billion, not $2.2 billion. That averages out to $76.8/year for each user, average monthly of $6.40. Which is notably less than the $10/mo rate in most parts of the world, even lower than the averaged monthly for an even split of both tiers ($12.50).
So, assuming that's 25 million concurrent, then we can basically say that at most, half of the 25 million are paying the full monthly rate (either tier) for the entire year. Or it could actually less than that even, meaning the remainder would be a mix of those paying lower rates in certain countries (such as India), maybe paying for a few months here and there, paying via the $1 conversion, using free trails (therefore, non-paying), or using Microsoft Reward points (essentially non-paying).
Also I though the 4% figure was just for GP-style subscription services, not services like PS+ (which has at least 48 million paying members so assuming the GP percentages held up (they don't), and there were only 24 million PS+ users paying a full year, that's still $1.44 billion/year. Then add in XBL Gold where again, take the GP percentages holding up (which again, they wouldn't; this is just for demonstration purposes) and assume XBL Gold has half the # subs as PS+, and all are somehow paying for the year in advance. That's another $720 million on top of everything else.
That's already $4 billion, and we haven't touched NSO, Stadia, or Luna. Not only that but it also screws up the GP numbers not to mention the actual revenue Axios mentions. So I doubt this includes non-GamePass subscription services in the mix.