Also TJ, you may also be able to help me here - I was looking at...

Also TJ, you may also be able to help me here - I was looking at some some product specifications from a manufacturer yesterday and I noticed that their product offerings had increased Tap Density as the d50 size specification increased. My understanding was that the smaller the spheres, the more tightly, and densely, the material could be packed which is obviously opposite to the product specifications I saw. Is there an inverse relationship between the size of the sphere and the difficulty in making it well rounded for packing purposes, or is my understanding of the process wrong?