Hi @abhishek_90 ,
That is nothing to worry about, don’t touch it; it makes a barely noticeable difference.
But, since you are asking, increasing the Roughness slider in the Diffuse BSDF makes an Object look ‘softer’.
A roughness of 0 uses the Lambert Shader, Lambert said (in 1760): “a diffuse surface looks equally bright from every viewing angle” That would be a ‘perfect’ diffuse surface and that doesn’t exist in the real world (but it’s cheap to calculate).
A roughness higher than 0, switches to the newer (around 1990) Oren-Nayar model, that takes the roughness of the surface into account and is thus more accurate (but the difference is often very subtle).
