pref round

If your first choice drops you then you automatically get your second choice regardless of where you are on their list.

basically:
Every chapter turns in 2 lists which include every PNM that went to their pref party: 1st list is only up to quota, 2nd list has everyone else that attended their pref party.
If you are on your 1st rank chapter's 1st list, you get your 1st chapter. If you are not, but you are on your 2nd ranked chapter's first list, you get your 2nd chapter.
If you are not on either chapter's first list, you may still get your 1st chapter if they have to go into the 2nd list to make quota based on where you are on that list.
If both chapters make quota before getting to you on their second lists you will be a quota addition to one of the two chapters based on a lot of things like where you are on their lists, their total, how many As they already have, etc.

If you list both chapters after pref, you are guaranteed a bid to one of them.
If you only list one chapter after pref and are not on their first list, you are not guaranteed a bid and are dropped.

If a chapter does not have quota after going through both of their lists, they can offer snap bid to girls who are dropped, and only the chapter and the girl offered the snap bid know she was snapped and not placed normally. Snap bidding ends on bid day. The most popular chapters are not going to have to do this, so DO NOT RELY ON A SNAP BID.