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>Would that situation above cause the user eat up four user licenses on the terminal server or not?
It will not. RDS Per user CAL will be only issued when user remotes to RD Session host(terminal server) and you can utilize the feature on licensing manager to track the usage of CAL.
Track your Remote Desktop Services client access licenses (RDS CALs)
https://learn.microsoft.com/en-us/windows-server/remote/remote-desktop-services/rds-track-cals
Thanks,
Jenny