Nowhere has it been said it will take 15 years to build(it's not been said that construction has started).
I don't think the number would only be one.China has a huge shipbuilding capacity.They would probably overtake South Korea in a few years as the world's largest shipbuilder.
The U.S., on the other hand, will still have all ten of its Nimitz carriers and three brand new Gerald R. Ford class carriers by that time.
At this rate the Chicoms might catch up in two or three centuries..