A script generated from that website shows that the Tor Project’s repository and GPG key are added to apt, so you’ll get updates for Tor from that repository.
In addition to that, if you select automatic updates the unattended-upgrades package will be downloaded and configured with this file:
https://github.com/flxn/tor-relay-configurator/blob/master/misc/50unattended-upgrades.Debian (if you chose Debian). As you can see, TorProject is one of the allowed origins, so the tor package will be automatically upgraded. Auto-reboot is turned-off. However, I believe that when tor is updated with apt it will restart itself.