Hello Andy Moses,
Thank you for posting in Microsoft Community forum.
A User CAL allows one user to access the server from any device, while a Device CAL allows multiple users to access the server from a single device. In your case, since you need three people to concurrently RDP into the server, you should purchase three User CALs.
The cost of a Windows Remote Desktop Server CAL 2022 is a one-time cost of $220 per User CAL. This means that each user who needs to access the server will require their own User CAL.
I hope the information above is helpful.
If you have any question or concern, please feel free to let us know.
Best Regards,
Haijian Shan