I think DM counts. And it seems to count only after you get GX coz I'm certain I've been well over 200 summons when GX comes and Aster did not show up right away or any short while after that. So I was like, f*** that I don't need him and go pvp in DM...with dark fiend deck. Before I know it, Aster mission pops out of nowhere even though I rarely visit GX world at that time.
unless the mission text specificaly says (GX) or (DM) it does not matter for all/any mission... also only... Chazz and Alexis have to be done in GX with lvl6/7.... Aster,Bastion(Jaden) can be done in GM