Customer Acceptance Functionality.

Hi,

Need clarity on following customer acceptance scenarions.

1. Customer Acceptance prior to billing, some goods not acceptable

 This scenarion have a step saying "CSR raises an RMA order for Credit".
 As invoice is not generated what credit this step is talking about. What exactly this step do?

2.Customer Acceptance after billing, full explicit rejection
 This scenarion have a step saying "CSR creates an RMA order referencing the rejected order line, with a line flow
indicating receipt of goods or scrap."
 What does this step do? Is this to give credit for the invoice generated and do the receipt of rejected items?