210-Pcs [# 6 5/16'' to 1-1/2''] 304 Stainless Steel Round Pan Head Phillips Cross Wood Screws Drive Self Tapping Drilling Screws Assortment Kit

Are these really an assortment of sizes? One customer review states that they are all the same size - #6 but he does not explain lengths.

What exactly does the #6, #8, etc. refer to?

Does the #6 refer to width of the head or the thickness of the screw length? I bought these but they are not 'thick' enough. Not worth return costs