The article is about an estimation of the total volume of transactions going through apps on the app store, both in the app store and outside of the app store direct to the app publisher. It's currently at 1.1 trillion, they're projecting given the growth rate it could be 2 trillion in 2 years. That is the figure being discussed.
While the comment you are replying to is wrong, this comment is also incorrect.
> this data includes payments which are not captured by Apple directly. In the words of the authors, “More than 90% of this figure originated from transactions that did not happen through the App Store, meaning that these amounts accrued solely to developers and other third parties, and that Apple collected no commission on them.”