Unable to Perform Expense Report Export for Duplicate Invoice

Some Expense Invoice which could not successfully be processed with "Expense Report Export", Following Message was found in log file 

l_invoice_num =2011EB-007

(Check Invoice Number 2) Check for Invalid Invoice Number.

(Check Invoice Number 3) Check for Duplicate Invoice Number.

(Insert Rejections 1) Insert into AP_INTERFACE_REJECTIONS, REJECT CODE:DUPLICATE

INVOICE NUMBER

I want to ask in which of these cases expense report export would work

1- Duplicate Invoice Number for Same Supplier

2- Same Invoice Number for Different Supplier