Unknown phone in my screen time

So I checked my screen time settings and was just messing around looking at them. I turned on “Share across devices” and then clicked on devices in the top right corner and a random phone that I do not know popped up. I checked with everyone in my family and it’s not theirs. I left the share across devices option on for a bit and saw no activity from this device so I eventually turned of the sharing option. I have not signed into my iCloud on anyone else’s device. Does anyone know why this would happen or has happened?