The company only updates seniority numbers in June. They go through the seniority list then and remove all of the retired pilots or pilots that have left for other reasons and re-assign seniority numbers based on the pilots on the list at that time. New hires have to be put on the list and given a number, so they simply add numbers to the list, even though there could have been pilots who have left. Could they do it monthly, I guess. Does it really matter, not in my opinion. The only thing that should matter is where you are bidding in your seat, which is updated immediately.

Thanks pinseeker

In simpler terms, They only update the Seniority List once a year (July 1).