If one were to look at previous vacancies awards you will see that if a person withdraws from their awarded position, the secondary award is no longer valid. Fortunately, there are usually other withdrawals within the category and the individual still ends up getting the awarded position.

Example vacancy 17-02
Initial Award LGA 900 Captain showed 7 primary awards and 13 secondary awards created by 13 LGA 900 captains bidding to other positions.

Final Award
5 of the original LGA 900 captains withdrew from their awards to remain as LGA 900 captains thus shrinking the secondary positions to 8. 2 individuals withdrew from an initial LGA 900 Captain award and 5 individuals awarded secondary positions also withdrew from their initial award. With the addition of one person returning to work being awarded a LGA 900 captain spot the individual who had the bottom spot for the initial award remained in the bottom spot in the final award.

Had more than the 5 original LGA 900 captains withdrawn from their awards, a corresponding number of individuals awarded secondary award would have lost their award. Had any of the 5 original LGA 900 captains opted to go with their initial award then secondary vacancies would have been filled with an alternate if listed, by the next in line despite not seen in the initial award or the company could choose not to fill the secondary vacancy.

Pretty complicated when you think of a Captain pulling out of an initial awarded position and the secondary effects.

Concerning the ATL 900 Captain positions, one can expect half of those to withdraw from the award as those that are pretty senior in their current base see they could be middle or lower in ATL and calculate they are much better remaining in their current position. There will be quite a few in the alternates that will withdraw as they see they can hold better lines where they are currently at. The outcome will see that the Atlanta 900 will have a scooped seniority list for captains with the top 25 being very senior pilots and the bottom 25 will be very junior captains. Some of those junior captains are probably not even on the alternate list at this time hence this warning message in the union's emails concerning Vacancies that you may be awarded even if your name is not on the list and you will not be able to withdraw from a final award.

As for the First Officers bidding to ATL 900, it will have a much more even spread as seen in the initial award. There will be less withdrawals on the First Officer side