Transact does not understand IP ranges. If you enter a range, only the first entry of the range is restricted. You need to insert each IP address individually.
The Transact API has IP restrictions at the Org level, which is pulled from the Acoustic Campaign user interface. Any IP address that is in the list is restricted, regardless of the status of the check box.
If you access an Acoustic Campaign Transact organization through the user interface, the system recognizes both the Organization Security Settings Access Restrictions and User IP Restrictions.