Earlier quoted context omitted.
Mostly, it funded development: http://venturebeat.com/wp-content/uploads/2014/11/mozilla_re...
In 2012 they had a surplus of more than $100,000,000 though... And still, $30,000,000 for administrative cost? $45,000,000 for marketing? (never saw any ads for firefox, did you? I have no idea what they spent so much money on)
https://static.mozilla.com/moco/en-US/pdf/Mozilla_Audited_Fi...
It isn't hugely informative, but I would guess that the $9 million in office leases mentioned towards the end is categorized as an administrative cost.