We don't really know what the interior of the Ark looked like, because there is no detailed description in the Bible of the interior of the Ark. This is what it could have looked like. So when Rod built his model he had to work out what it could have looked like, based on the needs of providing space for animals. The entire model is built to scale.

In this picture you can see some of the animal stalls and feed storage areas. The picture of Rod is also the correct scale so you can get a comparison.