Risk limiting election audits?

Came across this rather outlandish claim in a Politico article Colorado launches election safeguards:

Quote:

Risk-limiting audits are cheaper and more efficient than older audit methods because they use statistical processes to select and analyze a smaller sample of ballots than was previously necessary. Stephanie Singer, the project lead at Free & Fair, told Eric that Colorado would only have to check 142 ballots out of the 2.85 million cast statewide in 2016 to determine whether the results were correct, compared to the 32,000 ballots required under a normal audit.

(Highlight added).

Anyone care to explain how this could possibly work?

via International Skeptics Forum http://ift.tt/2t9j4z9