What does unlimited 1 session mean?

I'm guessing it means one client at a time, but to me could also mean can only run it once, but for an unlimited amount of time.

Sorry if this is dumb, I really have no idea. Thanks for the help in advance.

 

One client, your key lasts forever and doesn't expire. Basically, you can use RB on one client at a time for the rest of time.

 

Thank you very much for the quick response!