Hello,
You receive this (non automated) mail because you once contributed, or still contribute, to the translation of Debian Installer in the above language.
The translation status for this language can be seen here:
http://d-i.debian.org/l10n-stats/level1/nn.txt
I would very much welcome if you update these translation and complete them.
The material is there:
http://d-i.debian.org/l10n-stats/level1/files/nn/
Some people in your team probably have commit access and know what to update and where.
If nobody does, then please send the update file(s) back to me so that I can commit them.
Thanks you in advance for helping your language to reach 100%ness in D-I!