The Amount Owed and Amount Overdue get updated against the account or contact record in Dynamics 365 whenever new synchronisation happens against that customer.
Amount Owed
The total Amount Owed by the contact in Xero is available on the Account and Contact record (not on an individual invoice). Click on the Customer and choose the ‘Connectorly’ view where it says Account/Contact.
Once in there, the area below Account Name and Invoice Name is shown - with Amount Owed:
Amount Overdue
The total Amount Overdue for a Xero Contact is shown in the same area as the Amount Owed, and is available in the Connectorly view: