Hey, what are you ranking AEPhi last for...
If you were on SDT's B list - if enough people from SDT's A list had matched to other sororities, you'd match to SDT, otherwise you would be held aside. They then make a second (third, fourth...) pass through the pref cards that are held aside. So if, by the second pass, enough people from SDT's A list had matched elsewhere, you'd match to SDT. If SDT had met quota, you'd match to AXiD because you're on their A list.