What size scoop did I receive?

Scoops are a crude form of measurement. They are reasonable to use for compounds like creatine or piracetam which are impotent, safe in overdose, and have a broad therapeutic window.

Scoops are not a reliable form of measurement for titrating a specific quantity. A milligram scale is available on Amazon for $20-$30. It's highly recommended that you rely on scales rather than scoops.

Why does the same scoop size deliver different amounts for different substances? The density of substances varies widely. For example, 0.15cc of lead is much more massive than 0.15cc of carbon aerogel (the lightest substance identified to-date). In the same vein, 1cc of aniracetam corresponds to 610 mg aniracetam (see table), whereas 1cc of piracetam delivers 1g. 

Fun fact: 0.15cc of "black whole" would contain 9 x 10^11 kg. 

Organic compounds have different densities due to the crystal structure of compounds (e.g., how they "stack" or their lattice structure).