Adell, your settings are typical Indesign document settings and seem to refer only to the inside work, not the cover.

The Dutch instructions seem to be about the (hard?) cover or the printed sheet to go around the coverboards, not the inside book block.
– total width 657 mm, total height 256 mm (netto trim size of book block 297 x 210 mm)
– width of spine 11 mm, height of back board 216 mm, width of board 293 mm, height of board 216 mm
– kneep is the hinge part between the spine board and cover boards (don’t know the English term) 10 mm on each side
– inslagen is part of cover wrapped around the edge of the board to the inside, so the wrap margin is 20 mm
– the cover board juts out 3 mm all around (oversteek)

So it strikes me that the settings don’t need changing, but work is needed for a cover.

Hope this helps.