Why copied value passes and entered from the keyboard is not? (Rules basket)

[maximP]

if you enter from the keyboard 1234, it displays an error message if you copy the displayed value is the error does not occur.

{if $voucherAllowed}
                 {if isset($errors_discount) && $errors_discount}
                                <ul class="alert alert-danger">
                                    {foreach $errors_discount as $k=>$error}
                                        <li>{$error|escape:'html':'UTF-8'}</li>
                                        {/foreach}
                                </ul>
                            {/if}
                            <form action="{if $opc}{$link->getPageLink('order-opc', true)}{else}{$link->getPageLink('order', true)}{/if}" method="post" id="voucher">
                <div id='vouch'>
                  <input type='text' placeholder="{l s='1234'}" id='voucher_number' value="1234">
                  <input  onmouseover="$('#vouch').css('background', '#F49232');" onmouseout="$('#vouch').css('background', '#43B51F');" class="addVaucher" name="submitAddDiscount" type="submit" type="button" value="{l s='OK'}" >
                </div>

                                <fieldset style='display:none'>
                                    <input type="text"  class="discount_name form-control" id="discount_name" name="discount_name" value="{if isset($discount_name) && $discount_name}{$discount_name}{/if}" />
                                    <input type="hidden" name="submitDiscount" />

                                </fieldset>
                            </form>
                            {if $displayVouchers}
// displayed coupon code
                                <p id="title" class="title-offers">{l s='Take advantage of our exclusive offers:'}</p>
                                <div id="display_cart_vouchers">
                                    {foreach $displayVouchers as $voucher}
                                    the code-->    {if $voucher.code != ''}<span class="voucher_name" data-code="{$voucher.code|escape:'html':'UTF-8'}">{$voucher.code|escape:'html':'UTF-8'}</span> - {/if}{$voucher.name}<br />
                                    {/foreach}
                                </div>
                            {/if}
          {/if}