Hi Tobias,

Thank you for contacting WPClever Support Forum. I'm on sick leave for some days so today I am able to reach back to you.

I have assigned one of our developers to help you with that. He’ll be looking into your question and responding with specific instructions as soon as possible. 

Please stay patient as we're having very heavy workloads, it might take some time for our developers to reach back.

While waiting for our developer, you can kindly provide us with a link to your published product, our developer will help you check the frontend and offer the custom CSS code to fix that.

Best regards.

Hi Tobias,

Please send me your website link, which already used our plugin then I can check and provide CSS code.

Please add below CSS code to WP-Admin → Appearance → Customize → Additional CSS:

.woopq-quantity-input-minus, .woopq-quantity-input-plus, .woopq-quantity .qty {
    border-width: 2px;
    color: #222 !important;
    height: 42px !important;
    line-height: 38px !important;
    min-width: 42px !important;
    font-size: 14px !important;
}
.woopq-quantity-input-minus {
    border-top-left-radius: 5px;
    border-bottom-left-radius: 5px;
}
.woopq-quantity-input-plus {
    border-top-right-radius: 5px;
    border-bottom-right-radius: 5px;
}

And the result https://www.screencast.com/t/93n91RD1Ls

You're welcome!

If you are satisfied with our plugin and support, please reward it with a full five-star ★★★★★ rating.
https://wordpress.org/support/plugin/wpc-product-quantity/reviews/?filter=5
Thank you in advance! <3