Simple question about world composition;

Hello guys, if I want to make a space game with a lot of levels on world composition like 50 and after get all of then aligned and into the right places, I was assuming that I just needed to delete the terrains of this levels to stay with the “composition mounted” but when I delete the inside terrain in any level this level lost position and seems to goes back to the center of World composition map… Is not supposed to be like this that I should try to make a big and empty “space” ?

Thank all and sorry for my bad English!