The inventory tab is accessible only by office manager user scopes. There are two tabs under this section.
The Phone Numbers, and the Phone Hardware Tab.
From the Phone Numbers section you will see all the voice numbers assigned to your account and where they are routed. The destination where the number is assigned to is where it will ring or land on. This can be changed by the admin at any time.
The Phone Hardware section allows you to see all the physical phones assigned to users. From here you can see if the phones are online/offline, see the server is assigned to, the type of phone assigned to extensions, the lines that are open and phone directories. You may also reboot the phones that are online from this section. This can be managed by the admin at any time.
See attached video for additional information.