how to add 3 days in unix time to unix timestamp

Question

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script>
      $(document).ready(function () {
        var bid = "https://api.etherscan.io/api?module=account&action=txlist&address=0x8e0CF94c62A51B4eF7cA660B26863872af59EeF5&startblock=0&endblock=99999999&page=1&offset=20&sort=desc&apikey=NB86HEZM6GG9HCHMZA8ITHPHIEEVU57STI";
        $.get(bid).then(function (res) {
         
          console.log(res.result[0].timeStamp);
        });
      });
    </script>

this will return unix timestamp for Thursday, July 21, 2022 11:13:01 AM and i wanted to 3 days to it so i added console.log(res.result[0].timeStamp + 86400 * 3); and it gives Thursday, July 21, 2022 11:13:01.259 AM same date but nothing added how can i add 3 days to that unix stamp + if can reduce that added date by current date, thanks. jackson