List of devices on Apple ID includes an HP laptop??

[Breadnroses]

That’s it really. How is this possible please? My partner was showing me his list of devices as he can’t get his old iPhone to update. My HP laptop is listed as a device of his.
Can someone please tell me how this is likely to have happened?

If he has signed into iTunes / iCloud whilst on the laptop.

Ah is that how? I don’t remember him ever doing that though.

Even checking email would list it