Oops, yes you're right, it is a percentage of the net. I suspect that the contract in question is a relic from the sixties, when Hollywood accounting was nowhere as sophisticated as it is now and a percentage of the net actually got you some money.
Where did what come from? (Keep in mind I've only seen today's ep from about half an hour in... when they started looking at the guy from solitary who died.) EDIT: Oh... uhm... THAT. Where DID that come from? And who the hell was the reporter?!