The 'extra' stuff is merely water molecules of hydration. Completlely standard for a chemical like this. You could drive the extra water off, but it's not worth it to do so. FWIW, I remember using anhydrous calcium chloride as a desicant in chemistry lab. It is very effective at taking up water, even in organic solutions. If you toss anhydrous calcium chloride on the sidewalk (it's those little white balls of ice melter) you'll notice that it will also absorb water from the air.
I seem to recall reading somewhere that this 'Tetrachemicals' brand is okay, but I don't recall the specifics. Might be best to at a minimum do an ammonia test kit on the stuff after adding some to a batch of saltwater.