Hi @tranef, thanks for the extra info. If you checkout the Unity Documentation @ https://developer.tobii.com/pc-gaming/unity-sdk/api-overview/
GazePoint.Viewport returns the gaze point in Viewport coordinates, where (0,0) is the bottom-left and (1,1) is the top-right corner of the UnityEngine.Screen. The values can be higher than 1 and lower than 0 if the user looks a bit outside the physical bounds of the monitor.
So the behaviour you are experiencing is to be expected. Please also ensure you have the DPI on your system at 100% that the pixel resolutions should match properly.