That is such a misleading way to say it...
It's not 70%, it's around 40%. But 40% on size of the market (by price). When you compare it to 4.2%, it makes it seems that the market share should be 4.2%. Which can happen if you turn the US in to an undeveloped country without the means to buy anything.
https://www.novaoneadvisor.com/insightimg/Pharmaceutical-Market-Share,-By-Region.webp