I guess it could mean numerous things. If you made a list of countries in a region, Norway would be sixth for some reason. Or if new countries were appearing in a region, Norway would be the sixth.
So, if she is not the sixth country to claim land in any region, is Norway the sixth country in a larger region (say Scandinavia?) to sign a pact or take a certain action?
This topic really encapsulates the (modest) shortcomings of Duolingo. One can go from Norwegian to English with far more ease than to translate into Norwegian. These numbers are tough...but required !