I think the table is attributing greenhouse to gases generally, not to man-made gases; as a result, water vapor wins. (OTOH, turning clouds into drinking water at scale would be a cool way to fight global warming and deal with drought at the same time. My understanding is that storm seeding has a pretty seedy history, though.)
Wikipedia puts (with some question about the citation) methan at 4-9% of total greenhouse effect contribution, and CO2 at 9-26%. (And then water vapor way above that, at 36-72%.) https://en.wikipedia.org/wiki/Greenhouse_gas#Greenhouse_gase...