It's 40 millions by paper, other sum goes to Hulk and the agent's network. If you don't know, when Porto bought Hulk from japanese club, money was given to lower-division uruguayan club Rentistas (firstly 5,5 mil for 50% rights, then another 13,5 mil for 35%) where Hulk never played or actually been to. That's why Chelsea couldn't buy him, because third-party deals are prohibited for english clubs, unlike in South. There is FIFA investigation on this and many other similar deals by the same highly influential agent.
http://www.bloomberg.com/news/2012-02-16/fifa-to-probe-56-million-soccer-player-trading-operation-that-netted-hulk.html