Billing Amount Not Shwong For discount item for PO search

I have created one saved search for purchase order.

--Criteria--
Type - Purchase order


--Results--
Name
number
Billing transaction:number
Billing transaction:Amount
Billing transaction:Amount(Tax)
formula currency:ABS({billingtransaction.amount})+ABS({billingtransaction.taxamount})

In one purchase order transaction, there are two discount item for billing transaction.

In result first discount line item showing correct as shown in record but second discount line item not showing Billing transaction:number (showing blank) and so remaining column also showing blank.

first discount line is of amount 7640 and second line item is 0.15.

Is any one tell me reason why its showing blank.