Overriding GP Premium woocommerce styles

I'm making a woocommerce site with GP that has custom frontend fields added before the add to cart form.

I'm having trouble styling the custom fields because of this css:

.woocommerce div.product form.cart>:not(.quantity):not(.single_add_to_cart_button) {
    width: 100%;
}

I'm trying to style the fields with unsemantic grid classes.

I'm not sure why this css exists, but the nature of the :not selector means it's near impossible to override without !importants or complicated css selectors.

Any advice?