Hi Jason,
Thanks for your question, our report "Device Inventory" will show how many machines that have been retired over the giving time.
But you are also able to see the machines under our new feature "Assets state", if you navigate to "Assets" and then from the filter change the value "Active Devices" to "Inactive Devices", the system will now show devices that we havn't seen for the last 30 days or devices that manually have been setup to be inactive.
Hope this answered your question.
Best regards
Claus Tjoerndal