In order to get results the device groups need to be defined: MS Documentation
DeviceInfo
| summarize dcount(DeviceName) by MachineGroup
| sort by dcount_DeviceName
| render columnchart with(title="Total Devices by MachineGroup")
DeviceInfo
| summarize dcount(DeviceName) by MachineGroup
| sort by dcount_DeviceName
| render columnchart with(title="Total Devices by MachineGroup")