[NTG-context] Layout questions

Hello! OK, thank you for your answers to my questions. Now another bunch, this time I started reading the section on layout in the manual. When using \setuppapersize with one argument, does it imply that the default value of the second parameter is equal to the first one? If I use both, does it imply that the "smaller" page (determined by the second argument) is centered on the real paper (with size defined by the first arg)? What do the options "offset" and "scale" for \definepapersize mean? Are there any other options other than these two and "height" and "width"? Thanks in advance and greetings -- Marcin Borkowski