The device policy of 'normal' just means that there is no specific Group Policy, Whitelisting or Blacklisting applied to the client. The device will follow the rules configured on the underlying infrastructure, e.g. the firewall, traffic shaping, IPS and AMP rules configured on the MX. You can override these rules by creating a Group Policy and applying it to the device.
It should also be noted that a Group Policy can be created and applied to a VLAN, which needs to be reviewed too - this is applied on the Addressing & VLANs page, and applies to all clients on the VLAN that don't have a specific Group Policy applied. (Clients being affected by a VLAN-based Group Policy show a 'normal' device policy).