Do CCN numbers have to be sequential or can it be the 8000# + HBL number if unique (no sequence)?

Do CCN numbers have to be sequential or can it be the 8000# + HBL number if unique (no sequence)?

The eHBL 8000 Cargo Control Number does not need to be sequential.  It can be any unique number, but it cannot be repeated within current + 3 years.