Unable to set default value

Hi,

I’m unable to set the default value.

[msdyncrm_twig]
{% form entity=”lead” mode=”create” default='{“leadsourcecode”:8}’ %}
<form method=”POST”>
<input name=”firstname” type=”text” required=”” placeholder=”First Name”>
<input name=”lastname” type=”text” required=”” placeholder=”Last Name”>
<input name=”telephone1″ type=”tel” placeholder=”Business Phone”>
<input name=”emailaddress1″ type=”email” placeholder=”Business Email”>

<button type=”submit”>Submit</button>
<input type=”hidden” name=”_key” value=”{{form.key}}”>
</form>
{% endform %}[/msdyncrm_twig]

Thanks for your help