you just need to pick one of those four
Outside of the VC industry, one technique used by some investment management companies is to launch enough funds that some will outperform the market by chance. Then they quietly close down all those that perform equal to, or worse than the market average and trumpet the success of the one or two that lucked out.
Perhaps which four of the thirty you should pick is only obvious with hindsight :)
or that Kauffman are bad pickers of funds
I assume when they compare VC funds to a "common stock index" they mean an index fund [1], a type of fund that aims to provide market-average performance with lower fees than an actively managed fund. For example, an index fund tracking the S&P 500 does it by holding all the shares that comprise the S&P 500.
[1] https://en.wikipedia.org/wiki/Index_fund