This article answers that references tracking the master bill of lading (or parent references) are not billable and only the child references tracking each container are billable
The creation of a parent reference based on a provided bill of lading is not billable.
To provide an example, a bill of lading that is used to track 10 containers will count as 10 active references only. The parent reference is used as a base to determine how many containers need to be tracked and each child reference will have its own unique reference ID.