That depends on the light switch, if it's marked [91] the 21W filament lights up both with the 4W filament if the light switch is in the "0" postion. Also the green "light bulb" tell-tale is always lit (mostly this bulb has blown already ) and the rear lights are always on.
If the light switch is marked [89], in position "0" only the 21W filament lights up.
This description fits LHD cars, don't know if the switch markings for RHD cars differ.