You can do a calibration in KODI.
1 – Open KODI app on your device.
2 – Now go onto System option and click OK on remote.
3 – Now click on System option at the bottom, once you are inside system option at bottom left side you will see Settings Level, make sure settings level is on Expert. If it is on basic or standard just click on it and it will change to advanced, click again and it will change to Expert.
4 – Now once the settings level is changed click on Video Output at the top.
5 – Now go onto Video Calibration and click on it and adjust your screen according to your Tv Screen, make sure the corner lines are visible.