Good news, they just divided the estimated amount of wealth by the estimated number of people in two scenarios.
Unfortunately, my tendency is to view it as bullshit, not because of the climate science, but because of the economic models, where mitigated climate change is depicted as a simple differential equation of reduced exponential growth and unmitigated climate change is rendered as the same thing but with a new factor in the form of supply chain disruption estimation, which is essentially derived from averaging 14 other published models that were designed to measure other economic impacts of climate change, but not exactly the ones this paper is assuming.
Basically, my objection is that supply chain disruptions are not exponential in nature, and there's an adaptive dimension to them such that their effects on the flow of economies is dampened by planning.