Man kan använda 2 resdagar i sitt hemland. Eftersom denna resa använder båda dina resdagar i Sverige så måste du köpa en vanlig biljett för resan i Sverige när du kommer hem igen.

Men jag har hört om en speciell regel för Sverige att du inte behöver använda två resdagar om du reser direkt till Narvik. 

Den känner jag inte till. Var har du läst om den? 

Du kanske förväxlar det med den norska regeln för de som bor i Nordnorge?

https://www.vy.no/alt-om-reisen/tog/billetter/interrail

Interrail Global Pass

Billetten gjelder i hele Europa, og du kan velge om du vil betale for et begrenset eller ubegrenset antall reisedager innenfor en gitt periode. Du kan velge mellom ti ulike varianter.

Hvis du kjøper en av Flexi-variantene, kan du selv velge hvilke dager du vil reise innenfor den totale gyldighetstiden.

Interrailbilletten gjelder ikke for reise i landet du bor i, men den kan benyttes for én utreise og én returreise i bostedslandet. Reisene må foretas innenfor billettens totale gyldighetstid, og gjøres i løpet av én dag.

For reisende fra Nord-Norge aksepteres det at det brukes to reisedager hver vei når dette er nødvendig.

Interesting. So how would that work on a mobile pass?

Purely a thought:

Do trains from Southern Norway run overnight and somebody in Norwegian Rail has interpreted the overnight rule in this confusing way? In other words a poor translation/interpretation.

No, the rule is there and I am now wiser than I was 2 months ago and the special rules with 2 outbound and 2 inbound travel days in special cases also applies for Sweden. With the paper pass there is no problem, but with the mobile pass you need to get the extra outbound/inbound days from Customer Support.

However, only some people at Customer Support seem to know of this so some travellers get the extra days and some don't. 

Thanks for the update.

Snälltåget has information about the possibility to use several trains over more than one travel day for the outbound/inbound journey. It doesn't say though how it is done practically with a mobile pass. 

https://www.snalltaget.se/destinationer/kontinenten/interrail

Maybe via Customer Service. This was a topic some times here, and they added days to people that live to far from the next border like nordic countries or also from Sicily to Switzerland is very long. 

This should be an official rule on the interrail website and not like now where nobody knows how it works.

I totally agree with you @Angelo