the scripts, physics and others execution time increase for low quality compared to good quality

Working on different games deploed on different devices (laptop, tablet, HTC and Galaxy S6), I used two type of qualities with the seeting below: Good Quality -----------------------------------------* Rendering: ------------------------------------------------- - Resolution: Full-screen - Pixel Light Count: 4 - Texture Quality: Full Res - Anisotropic Textures: Per Texture - Anti Aliasing: 4x Multi Sampling - Soft Particles: Activated - Realtime Reflection Probes: Activated - Billboards Face Camera Position: Activated

----------------------------------* Shadows :--------------------------------------------------------- - Shadows: Hard Shadows Only - Shadow Resolution: Medium Resolution - Shadow Projection: Stable Fit - Shadow Distance: 50 - Shadow Near Plane Offset: 2 - Shadow Cascades: Two Cascades - Cascade Splits: (33,3%, 66.7% )

--------------------------------------------* Others:--------------------------------------------------- - Blend Weights: 2 Bones - V Sync Count: Every V Blank - Lod Bias: 1 - Maximum LOD Level: 0 - Particle Raycast Budget: 256

Fast Quality -------------------------------------------------* Rendering:------------------------------------------------ - Resolution: Full-screen - Pixel Light Count: 0 - Texture Quality: Eighth Res - Anisotropic Textures: Disabled - Anti Aliasing: Disabled - Soft Particles: Disabled - Realtime Reflection Probes: Disabled - Billboards Face Camera Position: Disabled

-------------------------------------------------* Shadows :------------------------------------------------- - Shadows: Disable Shadows - Shadow Resolution: Low Resolution - Shadow Projection: Stable Fit - Shadow Distance: 15 - Shadow Near Plane Offset: 2 - Shadow Cascades: NO Cascade - Cascade Splits:0

--------------------------------------------------* Others: --------------------------------------------------- - Blend Weights: 1 Bone - V Sync Count: Don’t Sync - Lod Bias: 0.3 - Maximum LOD Level: 0 - Particle Raycast Budget: 4

So my Question is: I would Like to know why the execution time for the scripts module, the Physics and Others increase rather than decrease, I know that it depends on the parameter seetings above but as you can see in the seeting I reduced these parameters for the Fast Quality, so can someone explains to me how this is working.

Thanks in advance.