I can't see the pattern because I don't have that book, but I would think from the description of the blanket that you are only doing a chain 24 foundation because this blanket is worked from the center outward. "Lacy clustered blanket crocheted from the middle in soft shades of Bernat Big Ball Baby Sport"
Having said that, you will be working something like a center round or block, then adding your rows around, getting larger as you go. When you get to the place where you "turn the corner" so to speak, you will have the 2 chain stitches that make the corner. Usually you will work stitches on the next round into that 2-chain corner space.
Again, I can't see the pattern, but when working from the center, each round gets larger, and you have to add some kind of extra stitches at the corners so that it continues to lay flat.....in this case it seems to be the extra chain stitches.
I would contact Bernat Customer Support anyway, if you are still confused.