How many users can the workshop have?
The package sets how many users the workshop can have: Basic 2, Pro 5, Premium 10.

In Settings › Users, permissions you see how many seats are taken and how many are free (for example "Users: 2 / 5 taken, 3 free"). A mechanic is a user too, with his own sign in. When all seats are taken, no new colleague can be invited; the program tells you what you can do. You can remove someone who no longer works in the workshop, or ask for more seats: the operator can give a workshop more.