Carnival doesn't just buy fuel at whatever the daily rate is at the local Citgo, they have huge contracts with suppliers. They probably negotiated a fuel contract when prices were at rock bottom.
That's where they expect the stock to be priced within a given timeframe, usually a year. The point is not necessarily the actual price they predict - but if that price is higher or lower than it is now, and by how much. That shows whether the analyst expects the company to be better or worse off then.