This value sets the default cache max age of new REST List and REST Multi List Parameters, in minutes. A parameter keeps the values of a successful fetch (all pages, after expressions, filter and order) in memory for its cache max age, whatever caching headers the endpoint sends; 0 means values are not cached and every request contacts the endpoint.
Cached values are kept per job, parameter and value source, for up to 1000 parameters, and are gone after a restart. Users can refresh a parameter's values on the build form, and Clear Value Cache below removes the cached values of all parameters without saving this page.