This is what the tomtom site says about the Africa map:
Detailed coverage: South Africa, Swaziland, Lesotho, Mauritius, Mayotte
Partial coverage: Nigeria (77%), Morocco (70%)
Connecting roads: Angola, Benin, Botswana, Burkina Faso, Cameroon, Congo, Gabon, Ghana, Kenya, Malawi, Mali, Mauritania, Mozambique, Namibia, Niger, Senegal, Togo, R?union, Uganda, Zambia, Zimbabwe
Coverage information: For the connecting road countries it offers detailed street network in major cities.
Roads covered: over 2.2 million km / over 1.4 million miles
Points of Interest (POI's): 376 000 Points of Interest
So, Nambia is in the 'connecting roads' category.