value

The value() method, called without any parameters, will return the numeric value of the NumericTextBox widget.
The value(newValue) method can be used for setting a new value for the widget.

<input id="numeric" value="10" />

<script type="text/javascript">
    $(function () {
        $("#numeric").shieldComboBox({
            value: 10
        });

        $("#numeric").swidget().value(20);

        console.log($("#numeric").swidget().value()); // prints 20
    });
</script>