I have a question about interpretation of R2.

The Economist has built a statistical model to identify what makes a country good at football: "What makes a country good at football?".

https://www.economist.com/international/2018/06/09/what-makes-a-country-good-at-football

In a apart of the article, it says:

Our model explains 40% of the variance in average goal difference for these teams.

Is it the interpretation of R2 in this regression: regression of average goal (per a match) of teams on GDP per capita, football’s popularity ........?

Or

Is it the interpretation of R2 in this regression: regression of average goal difference (per a match) of teams with respect to median team on GDP per capita, football’s popularity........?

I am sorry for asking such a simple question but I am really confused about it.

I would be really grateful if you could possibly guide me about it.

What about the following interpretation of R2:

suppose we regress the GDP per capita of countries on, for example, their inflation rate. suppose the R2 of this model is 50 %.

Can one say: 50 % of the difference between GDP per capita of countries is due to the difference between their inflation rate?.