Exported item sales from seller dashboard and saw this unique payment id Pd3M9l7z7qNVBGsZwshTi5FluaB, vFX4wOhLP2OoQU0BiEOvcISMuaB. However, I get both these payment IDs via payments API as individual entries and has the same amount. Is this a duplicate or a bug in payments API.
Those payments are for the same order vpB9zhx7WXWLfFDoeC5SMpkeV . One is a partial gift card payment and the other is for the remaining amount owed for the order. 
So what should be the total value ? 11.5 + 11.5 or just 11.5?
The total amount owed was $11.50. One payment was $8.50 and the other is $3.00 to make the total of $11.50.
I guess the problem is that both the payments are linked to same order. Hence if I want to get the gross sales at item level, I would end up seeing same numbers twice. And, I don’t see a gift card sales for this order, are you sure it’s a gift card sale?
I’m not following. Why would seeing multiple payments to complete an order be the issue? Often time there may be more than one tender used to complete an order. If you want gross sales at a line item level it would be the total of the all the payments that make up the order split between the line items minus any tax.