FR24 username: where is it displayed and who can see it?

I have a Premium account, and in the 'Your Account' section of the website there is a 'Change username' page that currently shows my username as NOT SET. What username is it and what is it used for? I already have my e-mail as username to log into FR24 Premium and it works fine, so I'm a bit baffled that it says Not Set. I'm tempted to set it but wonder who can see it and whether it is shown alongside the location of my feeder, in which case I would choose a rather anonymous username.

Thanks for the clarification!