Go to CCS>Help>Seniority trip trade. It is dated Dec 2015. 9:00 the day prior is the last STTS run for a trip. The 10:55 run is a real time SENIORITY based run for Lineholders and Reserves. It honors seniority as of late March. There is also a "first look" run. It's complicated. See the MEC update dated March 24th.

disclaimer....this is my take on the system. I am not on the SSC, but I did stay at a Holiday Inn last night.