Why does it not remove from list?

I have a App State list and a Double App State. To this App State called kortingBedragSlijterij, i give a certain value:

After the value is set to the app state kortingBedragSlijterij, i want to remove it from the list App State winkelmandTotaalPrijdSLijterij:

However, it does not remove anythin. Nothing happens. I tried everything, but it still does not remove the value of kortingBedragSlijterij from the list. What can it be? It sounds and looks really simple, but still it does not what it needs to do. Any ideas ?