You made a very good observation regarding sales of the packs. That thought never occurred to me. But would better explain sales rankings of individual items on BodyBuilding.com
In retail, individual and dual packaged items are inventoried, accounted for, and sold separately. For instance, candy bars at a grocery store. 6 pack of Hershey bars have a different SKU coding than the individual bars. They're listed as 2 separate purchases on the sales receipt, and sales are accounted for in the same manner.
Without knowing the sales figures of the packs it would be impossible to determine whether actual Muscle Pharm sales are up or down based on BB.com rankings.