Quantities on all-products page

Hello,

This plugin works great on the single-product page, but I also have a quantity selection option on the all-products page.

When I try to add (for example 6) pieces at once, the system only adds 1.

Any idea how this could be solved?

Here’s the link to my all-products page:
http://digistefbe.webhosting.be/kvins/shop/

Thanks in advance!

https://wordpress.org/plugins/woocommerce-incremental-product-quantities/