Florina campaigned on this number last year. When it was fact-checked, the conclusion drawn was Florina was obfuscating the term "Foundation".
A lot of Foundations started by individuals are pass-through organizations that do a wonderful job efficiently funding other charities but don't do much direct charity work themselves. The Clinton Foundation is a bit of a misnomer from this perspective because it implements a lot of charity work itself. So there's the 5-6% the Clinton Foundation sends on to other charities, but there's also the 75-85% the Clinton Foundation uses to implement the Clinton Health Access Initiative, Clinton Development Initiative, etc. If you treated those implementation arms as their own separate organizations, the Clinton Foundation would grade out at around 80-90% of their budget going to charity depending on the year. There are leaner charities, but 80% on a "bad" year is pretty damn good for as ambitious as the Clinton Foundation's goals are.
I'm not going to say the Clinton Foundation is above reproach or that the Clintons themselves don't even indirectly benefit financially from it. However, in terms of this election, criticizing the Clinton Foundation's efficiency is pretty damn brazen. I suggest reading
this Altantic piece about the Trump Foundation.
