component.html

<form>
  <label>
    <input type="radio" bind:group='interval' name="interval" value="monthly">
    <span>Monthly</span>
  </label>
  <label>
    <input type="radio" bind:group='interval' name="interval" value="yearly">
    <span>Yearly<span>Save 20%</span></span>
  </label>
</form>

data.json

{"interval":"monthly"}