Avast One Network Scan finds a new device that my router can't see

So, I started my PC and Avast one told me there’s a new device on my network that I didn’t recognise, but it didn’t show up on my router, I turned of the WiFi (despite it not being connected on my wifi and only my PC is connected with an ethernet cable. The Unknown Device still exists in the Network Scan. Is this just the Scanner not being correct?