Polycount goes to Triangles.
Both the OP screenshot and the NifViewer screenie display triangles counts.
The one you get diplayed in NifViewer is what the game engine must handle in the end.
The difference between what the author seen in max and what he ended up having in the export is because of a pecularity of the exporter.
@GeS - try exporting "Not Stripped", it should give you the same polycount on the exported file as you see in max.
Stripifying geometry does improve the perfpormance a bit (a document firaxis released says something around 20% - IIRC). It does however also increase the polycount - usually just a bit, but on some models (usually those having a bit higher polycount in the first place) the increase in Polycount will be huge. Obviously 20% performance improvement is egalized by 500% polycount, so it is better to skip stripifying.