Question about decrease in cabin rate with airfare

[kdgteacher]

I have a question that may seem confusing. My DH and I are booked on the April 7th sailing aboard the Serenade. I checked today and the price dropped a good bit. However, when I called RCI and asked for a credit they said that the airfare (which I also booked with RCI) has increased and even thought the cabin price has dropped $300pp the airfare went up from $299pp to $619pp. Making the credit only $120 vs $600+. I have already been assigned my flights by RCI and do not understand why after already having flight assignments I would have to pay an increase in flight just to get a rate change on the cabin. I am still saving $120 (which don't get me wrong, I am happy about) but I was just wondering if this has ever happend to anyone else or if this seems right. I am wondering if I should call RCI when they open in the AM to clarify this. Thanks!!!