How to read document numbers
ContentID
The document number, which is typically generated within your ERP source system, is expected to be sent as part of the commit request and is usually the invoice number. For a calculated request, this element isn't exposed in the API; thus, the document number's autogenerated by Determination. You can find this number in the contentId column.
ContentID

LineMessages
This shows the line messages number "8" after the ContentID. These messages get numbered as they're generated, but they don't always arrive in order.
Line messages
