Assembled on a Friday afternoon? I think the breaker they use in some models would fit either way, but being in a N3R enclosure there is a definite top and bottom to the enclosure. Some indoor load centers you do have to turn the main breaker around if it is not oriented to your application (bottom feed instead of top feed). This mostly only applies to three phase indoor load centers these days as single phase main breakers typically have a horizontal moving switch anymore.