The grammar explanation for this chapter says that the adjective small is the most irregular one in Norwegian. They recommend learning the table from memory. This seems impractical so the best I can say is it's one of those strange linguistic anomalies that you just "get" after seeing it in context over and over. English has tons of those irregularities.
Thank you so much. I have BEEN wondering this and WISH they would have allowed a "discussion" on the sentence that had a drop down choice between liten and små, but they didn't both times I ran through the exercise. Now I see it, it makes so much more sense. I find a LOT of my ENGLISH language rooted deeply in many of these Nordic tongues, and am enjoying studying them immensely. Grateful for that help, have a lingot, and Tussen Takk!
Thank you. Effectively I used wiktionary to control. I have found another site to control words but there wasn't a plural form written. I still haven't found a '' paper'' dictionary in my native language...But I will control later on different websites. Anyway tusen takk for your answer :)