The article focuses on universities' investments in hedge funds specifically. The numbers in the article suggest that on the high end, about 10–20% of an endowment will be in a hedge fund.

The question I have is, what are the typical returns just on that 10–20% investment?

The endowment can do poorly (as bad as or worse than an index fund) as a whole, even if the investment into hedge funds is paying out well.