Fixed a few issues in the shader. First of all the border mapping wasnt complete and I forgot the top and left side of the LEDs.. Also removed Typos. I also added sRGB and improved the saturation handling as before they didnt match accurate. I fixed it by the colors to linear space before processing them.

Before:

float luma = dot(rgb, float3(0.2126, 0.7152, 0.0722));
rgb = saturate(lerp(luma.xxx, rgb, saturationBoost) * brightness);

After:

sum += ToLinear(desktop.Load(int3(pixel, 0)).rgb);

float3 rgb = ToSrgb(sum / (samplesAcross * samplesDeep));
rgb = saturate(BoostSaturation(rgb) * brightness);