I am stumped as to how this could have happened. Then again, I have had some dealings with them and have been given wrong information too. Not sure if there would be any type of compensation for the window size, and sorta doubt it. Sometimes they will give a price adjustment or Future Cruise Credit for screw ups.
Again, this could have been a misunderstanding of terminology regarding the window. My best advice is not to let it ruin your cruise. And in the future use a CLIA or Carnival Certified Cruise Specialist Travel Agent when booking.
A CLIA affiliated agent can be found HERE.
A Carnival affiliated agent can be found HERE.
These folks work on your behalf and look after your best interests and are compensated by the cruise line, not you. So it doesn't cost any more to go through someone with more in depth knowledge of cruising or the particular ship you are booking.
It's not my intention to diss PVP's in any way. It's just my belief that dealing with a Travel Agent that specializes in cruises will be of better service in the future for this type of situation and most likely avoided.