I havent tried it but my guess is that it works like setshape2 where you place the 1 for new order simply put this {} then each number will set the tile type for each tile of 16*16 pixels like
PHP Code:
addtiledef 4x4chair.png,test,1{3,3,3,3}
will make a 64*64 pixels tileset (4 tiles) act like a chair only.
so if stefan could read this and tell me if im right or wrong, it would help =P