When the device goes OFFLINE, the NetLinx master will notify Offline for every port from 1 up to the maximum numbered port of any previously connected device that had used the same DeviceID - consider it an AMX-ism.
What this means is that you may get more device-ports being reported OFFLINE than are actually defined in your TP4 file.
1. Reboot your NI
2. Connect using the 7-port TP4 (file here) - you will see 7-ports come online
3. Make the device go offline - you will see 7-ports go offline
4. Load a TP4 file with say 10-ports (file here) - you will see 10-ports come online
5. Make the device go offline - you will see 10-ports go offline
6. Connect using your 7-port TP4 file - you will see 7-ports come online
7. Make the device go offline - you will see 10-ports go offline
The same occurs irrespective of the ICSP device (AMX or TPControl).