I would think overhead would be the 7.3% cited on Charity Navigator and the 22% fund raising would be separate. Maybe that 22% will really pay off in the future. If Bill likes them though they can't be doing too bad.
GiveWell is a much better evaluator of charity quality. Since they spend much more time on analyzing each charity, they cover way fewer charities. They are quite strategic about prioritizing which ones to interview. http://www.givewell.org/international/process