javascript setinterval function

Hi,
Advance thanks for the efforts.
I am using setinterval in the javascript. The confirmation box appears exactly after 10 seconds (which is good) . But if i wait for 20 seconds, i could see one confirmation box and it doesn't matter which button (Ok or cancel) i click, i see other dialog immediately (instead of waiting another 10 seconds, the box appears immediately)

window.onload = function () {
                    setInterval(function () {
                    var r = confirm("Click OK to continue your session. Click Cancel to log out.");
                    if (r == true) {                       
                    }
                    else {                      
                        window.location.href = '@Url.Content("~/")';
                    }
                }, 10000);
            };

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Also is there any way change button text 'Cancel' to 'Home'

Kind regards,
Pooja