Radiobutton Checked value return "on" instead of true

Quote:

For radio buttons, KO will set the element to be checked if and only if the parameter value equals the radio button node’s value attribute or the value specified by the checkedValue parameter. In the previous example, the radio button with value="almond" was checked only when the view model’s spamFlavor property was equal to "almond".

When the user changes which radio button is selected, KO will set your model property to equal the value of the selected radio button. In the preceding example, clicking on the radio button with value="cherry" would set viewModel.spamFlavor to be "cherry".