This might be related to the fundamental of the periodic boundary conditions. Mathmatically, f(y+d)=f(y). this means the unit cell repeats its self, by shifting a period from each other. In your case ,suppose currently this is the center unit. for the +1 unit, it begins from the larger and then the smaller cube.eg, the whole device will be "large, small;large, small;..."
It is just a shift, not a refection.
You can group them, then use "array" to create 3 units so you can see what it looks like:
if you have questions on how to use the "array" function and what do those parameters mean, please write a new post.