Mutliple devices in Microsoft Family

Looking for help with why multiple devices are showing up in the "My Devices" section of Microsoft Family:

Our household has one Xbox (an Xbox One S), and I set it up under our Family microsoft account, with a child's sub-account.

I was checking in on my child's screentime today, and am a little suspicious that he is being honest with me, so I dug a little deeper by logging in to Microsoft Family from my desktop computer (I usually check from the iPhone app).

My thought was that I would check to see if a new account or device had been set up secretly, so that he could get around my screentime limits.

Everything seems fairly locked down -- he can't start any games unless he is logged in as himself, and then I see his activity.

HOWEVER, I am a little miffed as to why multiple Xbox Ones are showing up in the "My devices" section of the Microsoft Family page. See below screenshot from that page:





These additional two devices have different serial numbers, and do not show our family account avatar.

Are these from other xboxes that he has logged into? For instance, at a friend's house?

Thanks in advance!

:)