{ +|- }{ MAJOR }{.{ MINOR }}
...
The minorversion field is optional. If not given, it will disable or enable
all minorversions for that major version.

[root@dell-r640-037 nfsdctl]# systemctl stop nfs-server
[root@dell-r640-037 nfsdctl]# nfsdctl threads 0
[root@dell-r640-037 nfsdctl]# nfsdctl version
+3.0 +4.0 +4.1 +4.2
[root@dell-r640-037 nfsdctl]# nfsdctl version -4
[root@dell-r640-037 nfsdctl]# nfsdctl version
+3.0 -4.0 +4.1 +4.2
         ^^^^^^^^^^^