I'm relatively new on the boards and don't always get the abbreviations/codes people use, but here's what I did recently...
I had a $100 voucher (coupon, if you will) because I was in a first class seat on an airbus and the audio/video didn't work.
I used that voucher to knock $100 off of a $244 non-refundable ticket, I purchased later. The agent told me that if I needed to make a change to the ticket, I'd have to pay the change fee, but the value of the ticket would only be $144, rather than $244, because of my voucher. Thus, subtracting the $100 change fee, I'd only have a value of $44 in the ticket.
$244 - $100 voucher - $100 change fee = $44 to use on a different flight somewhere.
Does that answer the original question?
[This message has been edited by grumpymonkey (edited 01-09-2002).]