Position of the woocommerce custom fields

For a client i’m making a webshop. Here she made an custom field wich needs to be underneath the other options. It comes next to each other. Anybody an idea how to fix it?

Here you’ll find the URL to see the problem: https://keukenfronten.com/product/arpa-fenix-bedekkingspaneel-paneel-op-maat/

Arpa Fenix kleur is the custom field.