The 2 device look like they are the name and the id of the same device. The number is the compressed without dots, IP address
For th test i made 2 groups with the same devices and they are discovered like this
20:41:32.360 [pimatic-sounds] Found ip: 192.168.1.44, port: 42897, label: Google Cast Group
20:41:32.361 [pimatic-sounds] Found ip: 192.168.1.44, port: 42494, label: Google Cast Group
To differentiate i can use the port number or the Friendly name should be there also