Now add a Bend modifier to the Master and play with its properties. You will notice that the Instance has now a Bend modifier applied to it as well. You will also notice the orange gizmo which is displayed on both objects in the viewport as well as the bolded names in the modifier panel. Everything that is bolded is shared between two or more objects.
Now Shift+move again one of the objects you have in the scene.
Set the new object as Reference and give it the name BoxReference.