Soil Grain size distribution

[Sebast_U_1973]

What logical assumptions could one make with comparing the D₈₀ grain size (Soil having > percentage finer than this size vs. a soil with the D₆₀ grain size being more dominant ?
Usually Sieve Analysis and material gradations reference the D₆₀ particle size and the D₁₀ particle size in order to obtain the C_u (Coefficient of uniformity) and also the D₃₀ is used in a formula for the C_c (Coefficient of curvature). So I was surprised to see a specification referencing the D₈₀, which in general would be smaller particles. (Comparing the same soil sample). Therefore, my question is what soil properties would this fraction of smaller particle sizes effect. Given a soil description of Silty Sand (USCS designation of SM). Would more smaller particle sizes effect the shrinkage factor, writer believes it would, aside from this property or behavior, this writer was searching for more definitive reasoning or output.

Any and all input is appreciated and look forward to summarizing a better conclusion on why this particular specification has referenced the particle size (D₈₀). Thank you for your time.