ทำยังไงโค้ดตัวนี้ถึงจะหาค่าอัตโนมัติครับ ต้องกำหนดตัวไหนอีกไหมครับ

<div class="bti-lm-clear"></div><div class="bti-lm-col-3-1">            <div class="field-wrap text-wrap label-above"  id="ninja_forms_field_297_div_wrap" data-visible="1">
              <input type="hidden" id="ninja_forms_field_297_type" value="text">
    
    <label for="ninja_forms_field_19" id="ninja_forms_field_19_label" class="">จำนวน <span class='ninja-forms-req-symbol'><strong>*</strong></span>       </label>
        <input type="number" min="10" max="9999" step="1" name="ninja_forms_field_19" id="ninja_forms_field_19" class="ninja-forms-field ninja-forms-field-calc-listen ninja-forms-req" rel="19" value="12"/>
  <div id="ninja_forms_field_19_error" style="display:none;" class="ninja-forms-field-error">
    </div>
              </div>
            </div><div class="bti-lm-col-3-1">            <div class="field-wrap calc-wrap label-left"  id="ninja_forms_field_20_div_wrap" data-visible="1">
              <input type="hidden" id="ninja_forms_field_20_type" value="calc">
    <label for="ninja_forms_field_20" id="ninja_forms_field_20_label" class="">ค่าใช้จ่ายทั้งหมด        </label>
      <input type="hidden" name="ninja_forms_field_20" value="1400" class="ninja-forms-field ">
        <input type="text" id="ninja_forms_field_20" name="ninja_forms_field_20" value="1400" disabled class="ninja-forms-field " rel="20">
        <div id="ninja_forms_field_20_error" style="display:none;" class="ninja-forms-field-error">
    </div>
              </div>
            </div>
<input name="_ninja_forms_field_6" class="ninja-forms-field " id="ninja_forms_field_6" value="สั่งจอง" rel="6" type="submit">
</div>
<div id="nf_processing_5" style="display:none;">
<input name="_ninja_forms_field_6" class="ninja-forms-field " id="ninja_forms_field_6" value="ดำเนินการ" rel="6" disabled="" type="submit">
</div>
<div id="ninja_forms_field_6_error" style="display:none;" class="ninja-forms-field-error">
</div>
</div>
<div id="nf_submit_5"><input name="_ninja_forms_field_6" class="ninja-forms-field " id="ninja_forms_field_6" value="ล้างข้อมูล" rel="6" type="reset"></div>
</div>
  </div><div class="bti-lm-clear"></div>  </div>
    </form>
    </div>
    </div>
    <div class="vc_empty_space"  style="height: 100px" ><span
      class="vc_empty_space_inner">
      <span class="empty_space_image"  ></span>
    </span></div>
    <div class="bti-lm-col-3-1">            <div class="field-wrap hidden-wrap label-above"  id="ninja_forms_field_27_div_wrap" data-visible="1">
              <input type="hidden" id="ninja_forms_field_27_type" value="hidden">
  <input id="ninja_forms_field_27" name="ninja_forms_field_27" type="hidden" class="ninja-forms-field ninja-forms-field-calc-listen" value="3300" rel="27" />
    <div id="ninja_forms_field_27_error" style="display:none;" class="ninja-forms-field-error">
    </div>
              </div>