I'm not really sure why this is post-worthy.

AFAIK, CO's systems view the two segments (LIS-EWR, EWR-LAX) as one flight, so the sequence numbers cannot be duplicated. So anyone on the LIS-EWR segment (regardless of whether they're continuing on to LAX) who checks in before you do will have a lower sequence number. They get a 10 hour head start for OLCI.