That’s in the same article where they compare the value of an endowment (measured in dollars) against the GDP of three random countries (measured in a different unit: dollars per year [per country]). Analytic rigor is not high.
I've seen this comparison in a few articles. It makes no sense at all. It's like if I said Microsoft's market cap ($1.942T) is larger than the GDP of Russian ($1.7T), or Apple's Market Cap ($2.125T) is double the combined endowments of every single US university altogether (about $1T). Complete nonsense comparisons.
It's interesting to note that Harvard could fund an entire country for a year.