“W” looks to be a user invited to the home, which gives that account access to yours, including Plex Pass benefits.
FYI, if these accounts pop up again and you did not add them, then someone has your account info and you should change your password ASAP. While you are at it, revoke any “device” under “Authorized Devices” and remove any device that you do not recognize. Might be good to revoke ALL devices on this page EXCEPT the “Plex Media Server” device (you don’t want to have to work at reclaiming your server).
What concerns me is that your home does not appear to have a Home Admin on that list. Is there more that we can’t see? Or perhaps you somehow accepted an invite to someone ELSE’S Plex Home. It’s pretty easy to accidentally join someone else’s home when they are just trying to invite you to view their server’s content. In which case, try to “leave” the home, and you will be back to your lonesome self.
