You set the region to the area where you use the car - different countries have different recommended service intervals. Your dealer can tell you which one they use, but you can always override it if you want. This only relates to when the idiot light appears on the dashboard, and nothing else.
JPN = Japan
NAS = (not sure if this is North America, or North Africa and Sahel)
EU = European Union
AUS = Australasia
GCC = Gulf Cooperation Council
Available settings are:
JPN10 - 12000 KM / 12 MONTH
JPN11 - 12000 KM / 6 MONTH
JPN20 - 12000 KM / 6 MONTH
JPN30 - 12000 KM / 12 MONTH
JPN31 - 12000 KM / 6 MONTH
JPN40 - 12000 KM / 3 MONTH
NAS10 - 12000 KM / 6 MONTH
NAS11 - 12000 KM / 3 MONTH
NAS20 - 12000 KM / 6 MONTH
NAS21 - 12000 KM / 4 MONTH
EU10 - 12000 KM / 12 MONTH
EU11 - 12000 KM / 12 MONTH
AUS - 12000 KM / 12 MONTH
GCC - 12000 KM / 6 MONTH
OPTION - OFF
Servicing is based on distance driven, or time elapsed since last service - whichever comes first.
Normal and Severe relate to the type of driving you do. If you drive on freeways t constant speed, and not a lot of short trips, it's called 'Normal'. If you idle a lot or do a lot of short journeys where the car doesn't warm up, it will be classed as 'Severe', and will need more frequent maintenance.