Active Directory Resync schedule does not remove unmanaged computers deleted from AD.
In ITMS 8.1 RU4 by default computers are deleted 7 days after removal from AD.
To delete computers immediately after resync;
Note: When ‘Delete’ action is enabled, we check out when affected resources were last imported by AD Import rules and only perform deletion to these, which are older than timespan defined by days in this setting. Computer deleted immediately if this setting set to 0.