Posting receipts from external system

We are trying to post receipts from an external system using the rcv_transactions_interface and rcv_headers_interface standard import tables. We will be processing the records in a batch mode (every 15 min) and we would like to know if the interface would process the transactions that result from a receipt followed by return to supplier and the the corrected receipt in the same order (or) is there some kind of manual sequencing number we need to supply to process them in that desired particular order.

Thanks

Ram