Is there a mistake in the product section for which card sleeves you need? The core set says you need number 5, while the expansions say you need number 2? Is this an error? /confused!

I think it is not size - it is number of packs U need to sleeve everything.

Core Set - 226 cards - 5x50 sleeves.

Chapter Pack - 60 cards - 2x 50 sleeves.

If You do not throw excess sleeves from coreset u can save Yourself purchase of one sleeve pack .

Ah of course. That makes perfect sense. I thought the number was related to the size of the sleeves! Thanks for the answer.

The size of the sleeves is indicated by the color...in this case grey (=Standard Card Game sleeves)