Change stock number upon option select not working

---NEVERMIND I FOUND IT----

Hello,
I have a question about a product and the options of that product.
If you go to this site:  kunsthumaniorabrussel.be/index.php/websh...insdag-29-maart-2022
When I select a product option at the select option "Kies een voorstelling" I want that the available stock amount of that option becomes visible, how do I do that?
Like in this example ( joomdonationdemo.com/eshop/product-layout.html ), when you select option "blue", availability goes from 70 to 24 

In attachment the stocknumber of the options available.

Thank you for your reply,
Greetings
Gerrit

 

Hello Gerrit Deschuyteneer,

It's fine that you figured out by yourself.

If you need any other helps, don't hesitate to let me know.

Sincerely, Giang