The only port open to the internet, assuming there was no prior misconfiguration done by the user, is the one for Roon ARC. You can disable the automatic port forwarding on your router if possible and active (uPnP and/or NAT-PMP). You can also disable Roon ARC making use of automatic port forwarding if you want to:
Update:
Alternatively and if you want to use Roon ARC.
Ask them them about the meaning/how to interpret the message they sent to you. Ask them about what to do or how you can disable the messages.