Nuts and cocoa also contain sugars, which make up the 5%. Those are the nutritional values, which state the total content - there is already some sugar in the contents before the sugar is added.

Math aint my strong suit either.
But it clearly tastes way better and other products in the same category (piemont hazelnut spread) taste very similar.
Thus I don't care enough to not buy it. It's not healthy to eat anyway and is bought for taste dn enjoyment ¯\_(ツ)_/¯