Outputting a countdown in a div
You may combine var statements and put them top of your function. Strip unused variables like parity and use element variable instead of using #defaultCountdown directly. And lastly, a little formatting will make your code much readable. Here is the result.

If you're trying to accomplish relative countdown, plugin itself supports it. I also put an example to show how to do it.

function stringToCountdown(selector, str){
    var hh = parseInt(str.substr(0,2), 10),
        mm = parseInt(str.substr(2,2), 10),
        ss = parseInt(str.substr(4,2), 10),
        austDay = new Date();

    austDay = new Date(
        austDay.getFullYear(),
        austDay.getMonth(),
        austDay.getDate(),
        austDay.getHours() + hh,
        austDay.getMinutes() + mm,
        austDay.getSeconds() + ss
    );

    $(selector).countdown({
        until: austDay,
        compact: true,
        format: 'dHMs',
        expiryText: 'No More Counter for you'
    });
}

$(function () { 
    stringToCountdown('#defaultCountdown','000010');
});


And this is less readable version. There is no extra variable. So it may run a little bit faster.

function stringToCountdown(selector, str){
    var austDay = new Date();
    $(selector).countdown({
        until: new Date(
            austDay.getFullYear(),
            austDay.getMonth(),
            austDay.getDate(),
            austDay.getHours() + parseInt(str.substr(0,2), 10),
            austDay.getMinutes() + parseInt(str.substr(2,2), 10),
            austDay.getSeconds() + parseInt(str.substr(4,2), 10)
        ),
        compact: true,
        format: 'dHMs',
        expiryText: 'No More Counter for you'
    });
}

$(function () { 
    stringToCountdown('#defaultCountdown','000010');
});