Как добавить к значению ползунка нужное число?

let sumText = document.getElementById("sum_text");
let sumSpan = document.getElementById("sum_span");
let sumSpan2 = document.getElementById("sum_span2");
let sum = document.getElementById("sum");
let summText = document.getElementById("summ_text");
let summSpan = document.getElementById("summ_span");
let summ = document.getElementById("summ");
sum.addEventListener("input", function () {
    sumText.innerText = this.value;
    sumSpan.innerText = this.value;
});
sum.addEventListener("input", function () {
    sumText.innerText = this.value;
    sumSpan2.innerText = parseInt(this.value)+169;
});
summ.addEventListener("input", function () {
    summText.innerText = this.value;
    summSpan.innerText = this.value;
});

document.getElementById("button").addEventListener("click", function (e) {
    e.preventDefault();
    localStorage.setItem("sum", sum.value);
    location.href = "form.php";
});
document.getElementById("button2").addEventListener("click", function (e) {
    e.preventDefault();
    localStorage.setItem("summ", summ.value);
    location.href = "form.php";
});

<div style="width:25%; float:left;margin-right:5%;border: 1px solid #888;padding:50px;">
<div class="calc_form">
  <form id="heroForm">
    <div class="flex_row form_el credit_count">
      <span style="color:#040404;">Сумма займа</span>
      <div>
        <span id="sum_text">3000</span><span> &#8372;</span>
      </div>
    </div>
    <div class="form_el">
      <input type="range" id="sum" min="500" max="20000" step="500" value="3000">
    </div>
    <div class="flex_row form_el min_max">
      <p>500 &#8372;</p>
      <p>20 000 &#8372;</p>
    </div>
    <div class="form_el flex_row">
      <button type="button" id="button" class="btn btn-submit">Получить деньги</button>
    </div>
  </form>
</div>
<div class="calc_info">
  <p><b>Возвращайте от <span id="sum_span">3000</span> ₴ до <span id="sum_span2">3169</span> ₴</b><br>с учетом всех комиссий и переплат.*</p>
</div>
</div>

<div style="width:25%; float:left;border: 1px solid #888;padding:50px;">
<div class="calc_form">
  <form id="heroForm">
    <div class="flex_row form_el credit_count">
      <span style="color:#040404;">Сумма займа</span>
      <div>
        <span id="summ_text">3000</span><span> &#8372;</span>
      </div>
    </div>
    <div class="form_el">
      <input type="range" id="summ" min="500" max="20000" step="500" value="3000">
    </div>
    <div class="flex_row form_el min_max">
      <p>500 &#8372;</p>
      <p>20 000 &#8372;</p>
    </div>
    <div class="form_el flex_row">
      <button type="button" id="button" class="btn btn-submit">Получить деньги</button>
    </div>
  </form>
</div>
<div class="calc_info">
  <p><b>Возвращайте от <span id="summ_span">3000</span> ₴ до 3169 ₴</b><br>с учетом всех комиссий и переплат.*</p>
</div>
</div>