Dockage means

Dockage means Impurity percentage of the seed lot.
Freshly harvested grain contains a small proportion of impurities, which is called dockage. 5.0% or less of the gross weight, assess as dockage.
Determine the percentage of dockage by combining and weighing all of the material which remained on top of the top sieve and which passed through the bottom sieve. The percentage is calculated by dividing the weight of the dockage by the total sample weight.