in my opinion, it's less so about the quantity of nuke china has, but more so about china's willingness to use them. Currently, china promised no-first-use regarding its nuclear arsenal, as well as promised no use of nuke against non-nuclear armed countries. Many countries in the world are counting on these promises; after all, nukes are useless unless there is a threat of using them. While it's true this promise shows good will, it also restricts the usage of china's nuclear arsenal. The only way to actually use nukes again a country such as vietnam is to break this promise, which would create a very bad precedent, and many countries would have second thoughts should china make any other promises in the future.