From the "Delphi 10 Seattle" documentation:
To specify a subnet of IP addresses, specify an IP address with a 0 as its fourth number. For example, if you specify "192.168.4.0" as the Target, your manager searches the 192.168.4.x subnet for remote managers. Note: You can not specify wider subnets. For example, "192.168.0.0" is not supported.