Expense Reports imported with different invoice numbers in R12

In iExpense module, 2 Expense reports created and imported to AP with addition to .1 at the end of expense report. But original expense report number invoices not created in R12.

There is no rejections and no exceptions. But we could see child expense reports are created for the parent ones.

Any one have idea on this why expense reports are not created with same invoice numbers in R12.