I haven't looked into it that closely but I don't think it's as clean cut as that. Personally I'm not really too bothered about which exchange trades what as long as I can see it. I use bookmap where it doesn't differentiate anyway and also I always seem to have more on that than is shown in DAS so it appears even with those exchanges DAS doesn't have everything. However, if you're curious, on DAS there's tabs below the L2 prices for the different exchanges you see. You can click across them and see what levels are on each exchange. The main one you look at is just combining them all basically.