I don't speak Dutch, either, but the following lines should give an indication to someone who does:
Algemeen: Aantal vakken voor hot-swap = 4
Uitbreiding: Aansluting/Bays = 4 (totaal)/4 (vrij) x hot-swap 3.5"
I would imagine that Mercateo would happily discuss different configurations (e.g. according to Davie's suggestions) with you, if you could tell them what exactly you are looking for. Good luck!