I have no idea if that number…283…is correct or up-to-date or where it is. To those wanting near real-time updates on the largest gaps between Superchargers there is a database for that. It started many years ago just for Interstates, but once that problem was mostly solved they moved to state highway routes as well.
See it here:
Someone posts every time a new Supercharger goes on line that splits these gaps
(Wild speculation: Elon just found out about how the Tesla community was keeping track of all this for “free”)
Mike