Each subscription comes with 3 users. This means that you can have 3 people using each subject at any one time. Each time you click on the launch button the program thinks that you want to launch it, so if you double click to launch the program, it will show 2 users, if you keep clicking it, it will fill up your user count, so it is important to only click once.
If your Gatekeeper is showing 3 users, and you are sure no one else is using the program, close down your browser for 5-10 minutes so that it resets itself.
Please note: It is recommended that you use the Cross button at the end of each session.