According to "Use of Stratified Sampling of Blend and Dosage Units to Demonstrate Adequacy of Mix for Powder Blends1" guideline
Identify at least 20 locations throughout the compression or filling operation to obtain dosage units. The sampling locations must be carefully chosen to represent significant events (e.g. hopper changeover) during the compression or filling process including samples from the beginning and end of the compression or filling operation. Take at least 7 dosage units from each location.
Please define 20 location of sampling point.