4bf911a6_l_Support___Transaction_fields__Description
[Field Name] kFirstTran [Type] Long [How Used] FKeyReq [Description] 
Key of first tran line for this doc. The first transaction line usually has a different set of fields than subsequent transactions - because it contains the totals. This will always exactly match the nKey field of a record in table TranLine.
DataBlox Technical Support - Transaction fields
Description