The Boeing 747-8 is a wide-body jet airliner developed by Boeing Commercial Airplanes. Officially announced in 2005, the 747-8 is the third generation of the 747, with a lengthened fuselage, redesigned wings, and improved efficiency. The 747-8 is the largest 747 version, the largest commercial aircraft built in the United States, and the longest passenger aircraft in the world.
It is the third largest version of 747.
In the context, the part saying "The 747-8 is the largest 747 version,..." proves that my entered statement is incorrect. I think what may have happened is the system got the "third largest" wording confused with the mention of "third generation" in the context.