Pop up time showing wrong

Question

Hi i am trying to open popup session expire before 15 min but when i set 120 min in webconfig then minutes is showing wrong minutes

 

so please help me

 

What I have tried:

$(function () {
$("#dialog").dialog({
autoOpen: false,
modal: true,
title: "Session Expiration Warning",
buttons: {
"Extend Session": function () {
ResetSession();
},
Logout: function () {
CloseSession();
},
Close: function () {
$(this).dialog('close');
}
}
});
});
function SessionExpireAlert(timeout) {
var minutes = timeout / 1000/60-1;
var seconds = 59;
$('#seconds').html(minutes + ':' + seconds);
var interval = setInterval(function () {

//var timer2 = $("14:59");
//var timer = timer2.split(':');
//by parsing integer, I avoid all extra string processing
//var minutes = 14;
//var seconds = 59;
--seconds;
minutes = (seconds < 0) ? --minutes : minutes;
if (minutes < 0) clearInterval(interval);
seconds = (seconds < 0) ? 59 : seconds;
seconds = (seconds < 10) ? '0' + seconds : seconds;
$('#seconds').html(minutes + ':' + seconds);
}, 1000);
setTimeout(function () {
//Show Popup before 900 seconds of timeout.//
$('#dialog').dialog('open');
}, timeout - 900 * 1000);
setTimeout(function () {
window.location.href = "../../../User/SessionExpired";
}, timeout);
};
function ResetSession() {
//Redirect to refresh Session.
window.location = window.location.href;
};
function CloseSession() {
//Redirect to refresh Session.//
window.location.href = "../../../User/SessionExpired";
};

Response.Cache.SetCacheability(HttpCacheability.NoCache);
if (!this.IsPostBack)
{
Session["Reset"] = true;
Configuration config = WebConfigurationManager.OpenWebConfiguration("~/Web.Config");
SessionStateSection section = (SessionStateSection)config.GetSection("system.web/sessionState");
var timeout = section.Timeout.TotalMinutes * 1000 * 60;
ClientScript.RegisterStartupScript(this.GetType(), "SessionAlert", "SessionExpireAlert(" + timeout + ");", true);
}

<sessionstate mode="InProc" timeout="120">