Editor API Emulation
One of the Ultimate Mobile features is an ability to emulate native Game Service responses while you testing your game with the editor. But you have to provide some data for the emulator to work with.
For example, you can specify the player id & name, or provide the list fo achievements & leaderboards. This is not a requirement at all, but if you want to be able to test the Game Services implementation right inside the editor, it's might be a good idea to set up the editor emulator data.
You will find this setting under the GameService module inside the Plugin Editor UI. The UI will look similar to the screenshot below: