Junior pilot on the property has a seniority number above 15,000. That includes all the pilots that are on different Leaves, so there aren't 15000 active pilots, but it gives you a good reference point for the rest of the discussion.

The junior pilot that is gauranteed a line for December in the 756 FO seat has a seniority number of:

DCA 12824
DEN 11248
EWR 13184
IAH 12437
LAX 13010
ORD 12732
SFO 13234

Given the crazy rate of hiring right now, that means that 756 pilots with a full year are prob just getting off of reserve on the coasts, getting close in DCA and ORD and then a couple more months in IAH and a little longer at DEN