Just guessing, and assuming they were relatively generous with equity since they seem like the type of company that would be.

I know AirBNB has let some employees take $ off the table in financing rounds. http://allthingsd.com/20111002/airbnb-investor-chamath-palih... My guess is that 0.5% is too high of a floor for post dilution and he probably had 10bps to 50bps at most