I'm confused as to what the Last IP field in the Viewer refers to. We use a self hosted server. As far as I can tell, all IPs in this field that I can see is either the WAN address on the network our self hosted server is running on, (for connections outside of our network) or a private IP address, possibly within our own LAN.
I would expect it to always either display the local IP address of the interface on the client used to connect to our self hosted server, or the Internet address from which our self hosted server receive the connection. Maybe both fields could exist.
The Last IP column shows the last IP address that was used by the given Host which is not necessarily the IP address of the Host computer itself. For Internet-ID connections, the Last IP address shows the IP address of the last used Internet-ID server, i.e. in this case - of the self-hosted server. Please note, that the private IP address is only shown in case if you use Direct connection within your LAN in order to connect to the remote Host, i.e. without an intermediary server. For more information on the column headings please refer to this Documentation page.