Question Xtrons Brightness Factory Settings Help

[Jackoliver361]

Hi I recently bought a Xtrons IA Series for my fiat 500. In direct sunlight it can very hard to see even with the slider on max for brightness. So I tired going into the factory settings using the code 8888 and clicking the display option. The brightness here is set at 4, however when I try to increase or decrease this value using the +/- buttons next to it the number stays at 4. Same with all of the other value too like contrast and saturation etc. Can these values not be changed? Any help would be much appreciated.