The metric Pixel Shader Duration represents an approximation of the total GPU time spent executing pixel shader code.
If Pixel Shader Duration is 50,000 it means that GPU spends around 50 milliseconds to execute pixel shaders for the selected ergs.
If Pixel Shader Duration is 0 it means that time spent in pixel shaders for selected ergs is very small.
Examine the Pixel Shader Duration time versus the GPU Duration; when Pixel Shader Duration is high you may improve overall rendering performance by optimizing your pixel shader code.
Check the Shaders Tab in the Graphics Frame Analyzer and examine pixel shader code to see if optimizations are possible. Refer to the HDG DirectX Developers Guide to find advice for pixel shader optimizations.