Subdomains have the default policy "None". If a subdomain's main domain has a Valimail enforced policy, the default policy of all subdomains is the policy of the main domain. This can be changed from the "Advanced Options" menu in the Policy pop-up:

There you will see the Subdomain policy setting:

As a side note the policy percentage should not be switched from 100% in order for the domain to be considered at Enforcement.

If you wish to change the policy on only specific subdomains, you will need to scroll to that subdomain in the configuration page and click on it. The change policy option will appear on the newly opened subdomain configuration page. This will only work if the specific subdomain points DMARC to us.

​NOTE: This option is only available for customers with the Enforce Premium package or higher.