What does the respective value of the APPROVAL_STATUS field in AP_INVOICES_ALL table mean?

Summary:

Hi,

To my best knowledge, The 'APPROVAL_STATUS' field in 'AP_INVOICES_ALL' table refers to validation status.

In BI, Running the bleow query retrieves the records below

Query :
SELECT APPROVAL_STATUS
FROM AP_INVOICES_ALL
GROUP BY APPROVAL_STATUS

Records retrieved :
CANCELLED
NEVER APPROVED
UNPAID
APPROVED
AVAILABLE
FULL
INCOMPLETE
PERMANENT
NEEDS REAPPROVAL

From the KM Note, I've learded the meanings for a couple of status as follows

APPROVED - Validated
NEVER APPROVED - Not Validated
NEEDS REAPPROVAL - Needs revalidation

But, I was wondering what the all the status above mean respectively

CANCELLED
NEVER APPROVED
UNPAID
APPROVED
AVAILABLE