72. satırdan süreyi ayarlayabilirsin.

<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1">
<style>
body {font-family: Arial, Helvetica, sans-serif;}

.modal {
  display: none; /* Hidden by default */
  position: fixed; /* Stay in place */
  z-index: 1; /* Sit on top */
  padding-top: 100px; /* Location of the box */
  left: 0;
  top: 0;
  width: 100%; /* Full width */
  height: 100%; /* Full height */
  overflow: auto; /* Enable scroll if needed */
  background-color: rgb(0,0,0); /* Fallback color */
  background-color: rgba(0,0,0,0.4); /* Black w/ opacity */
}

.modal-content {
  background-color: #fefefe;
  margin: auto;
  padding: 20px;
  border: 1px solid #888;
  width: 80%;
}

.close {
  color: #aaaaaa;
  float: right;
  font-size: 28px;
  font-weight: bold;
}

.close:hover,
.close:focus {
  color: #000;
  text-decoration: none;
  cursor: pointer;
}
</style>
</head>
<body>

<h2>Demo Site</h2>

<div id="popUp" class="modal">
  <div class="modal-content">
    <span class="close">&times;</span>
    <p>Demo içerik</p>
  </div>
</div>

<script>
var modal = document.getElementById("popUp");
var span = document.getElementsByClassName("close")[0];

span.onclick = function() {
    modal.style.display = "none";
}

window.onclick = function(event) {
    if (event.target == modal) {
        modal.style.display = "none";
    }
}

function PopUp(e){
    if (document.cookie.indexOf("popupGoster=true") == -1) {
        document.cookie = "popupGoster=true; max-age=86400";
        modal.style.display = "block";
    }
}

window.onload = function(){
  setTimeout(function(){
    PopUp('show');
  },25);
}
</script>

</body>
</html>