My cats get some Merrick's Purrfect Bistro dry and it too has powder leftover at the bottom of the bag. As @mrsgreenjeens said, probably most dry food bags are like that.
I think every dry food has it - even other animals' dry food. All the kibbles I've seen from low end to high end have powder at the bottom of the bag. My birds' pellets (of all brands) have all that pellet dust at the bottom too. I think it's partly from processing (where pieces are more fragile and aren't the same size), the friction of the pieces rubbing together, and just residue from machines while filling the bag. It's like when you have chips and there's all those powdered, broken chip pieces at the bottom of the bag (I still eat them!).
Once again, thank you all for your input. It is definitely the brand, though. I have fed my cat dry food before, and I have never encountered this issue. It is more than simple processing. Also, I read some reviews on Petsmart's site, and there were quite a few posts which mentioned an unusually high amount of food powder in their bags, too. I am thinking I will transition back to the other food brand.