Why is personal hotspot being used by unknown devices

I use my personal hotspot to connect to my laptop. It shows that my laptop has used 13.3 GB, Other Devices has used 12.3 GB, and 20214289 has used 19.3 GB. (I have no idea what the random number is.) Seeing that my password is too difficult to guess and has never been shared, and I work alone so there's no one who would be using it, what is causing the non-laptop hotspot usage? (I don't own any other apple products.) Are these numbers just a mistake?