$(document).ready(function () {
     $(".quantity-adder .add-action").click(function () {
         if ($(this).hasClass('add-up')) {
             var text = $(this).parent().parent().parent().find("[name=quantity]", '.quantity-adder')
             text.val(parseInt(text.val()) + 1);
         } else {
             var text = $(this).parent().parent().parent().find("[name=quantity]", '.quantity-adder')
             if (parseInt(text.val()) > 1) {
                text.val(parseInt(text.val()) - 1);
             }
         }
     });
 });
I added the .parent() so that then find the proper text to increase
7
solved How to individually increase or decrease a value using jquery