When the initial order we receive from the retailer has changes, we are sending a change acknowledgement to the retailer which includes all the changes made to the order. 

Based on the retailer setting PO Change Flow POC -> POA, once the change acknowledgement is sent we need to wait for the change response from the retailer (A change response is the document we receive which accepts the changes made to the order)

So when the system finds a change in the order it sends a change acknowledgement and change the order status to AWAITINGSENDCHANGERESPONSE. The order proceed to the next step when a change response is received. But there is another retailer setting "PO Change Timeout" which determines the time the order waits for to receive the change response. For example if the PO Change Timeout is X the system waits for the response for X amount of time, and if it doesn't come it assumes that the retailer accepts the change and proceed to the next step of the order.

This means that when the order status is on AWAITINGSENDCHANGERESPONSE it waits until it receives the Change response or until it reaches its specified timeout to proceed further.