Your Financial report shows the form of payment for every ticket. A credit card shows its code plus the last six digits, cash shows as CASH, and anything else shows exactly as the GDS stores it. The value comes straight off the ticket, with no translating or re-deriving.
The column appears in three places:
Next to Total Cost you also get a Total Cost To Customer column. Total Cost is base fare plus tax, Total Cost To Customer is the full amount you charge, so the gap between them is what you added on the invoice. On Display by Trip the figure covers every active ticket in the booking, so the two columns compare directly.
A ticket with no form of payment in the GDS shows a dash on screen and stays blank in the export.