The Dialing Restrictions shown in the UM Dial Plan are specific to calls made to the Subscriber Access attendant, while the settings in the UM Auto Attendant are specific to calls into that attendant. The UM Mailbox Policies are an additional layer that can be used to create multiple layered policies to apply to different users assigned to the same UM Dial Plan. you can either simply inherit the Dial Plan's settings in a policy, or create customized settings and additional policies.
The simplest scenario is to leave the Default Policy to match and inherit the Dial Plan's settings, and then configure the AA to the same settings as the Dial Plan to give users the same experience whether they are calling the main AA or dialing into the SA.
Jeff Schertz, PointBridge | MVP | MCITP: Enterprise Messaging | MCTS: OCS