ᐅ Ikea Matrand mattress cover: which side goes up?

Good morning, I just had to wash the cover of my Matrand mattress because of a coffee accident. Unfortunately, I didn't remember which way the cover goes back on the mattress. There is one side with holes and one side with foam... which one should be on top, the sleeping surface?

I am familiar with mattresses where the padding is on top inside the cover.