You know when Sayid and Jack(think it was them) tried to accesses the space behind the concrete wall and the key jack has around his neck was drawn towards it(M-field)? That’s probably the spot marked with an ‘X’. This was done before the person drew the wall painting. So it was after the instruction video was made (mentions measures taken). At the swan you can see 5 'X'. Where 2 of them mark where the swan has been sealed from it self (parted in two). Has some one been sealed in the other part of the swan?