They're emphasizing to bid where you want to be on this bid, and make sure to fill out your displacements as well. Proffers to displace are key and don't incur a training freeze or seat lock.
The union doesn't know how far it may possibly go up the list in reverse order because they don't have every pilot's flight time, but their back of the napkin is that it is possible it could go up to two years of seniority.