book purchase and $25 ship board credit

I bought a book called Alaska by Criuse Ship. In the back is a $25 coupon for shipboard credit for any HAL cruise to Alaska. This is one $25 credit per cabin. We have two cabins.

Of course, when I presented it to my agent AND also asked her if the price of my cruise has dropped, she said I can either keep my group rate and I could apply the $25 shipboard on one of the cabins, or move the type to a "60 day promotional sale rate" and drop the price by $25.00 per cabin. (We have two cabins) Since the movement to the 60 day sale would drop it for both cabins, I took that.

I was wondering if anyone else has problems in redeeming this coupon.

For anyone that knows any travel agent rules, the certificate has "rule # 9005 promo code # 7062.Combinable with early saving, mariner saving, standard group saving and group express.But MAP, "on Stage Alaska", etc, may not be combine with ship credit.
Upgrade such as one day sale, one week sale, one months sale are combinable.

Was my agent telling me the truth?