Well, since it's based on a true story, it might focus on a particular incident or series of events at a dog pound. It could be about a dog that was mistreated and then rehabilitated, or perhaps it's about the challenges faced by the dog pound in terms of overcrowding, lack of resources, and how they overcame them. It might also include stories of the relationships that form between the dogs and the staff or volunteers at the pound.
It's possible. There could be a case where a dog with a rare breed was in the pound and attracted a lot of attention from breed enthusiasts all over the world. This led to not only the dog getting a great home but also brought more awareness to the dog pound and its needs for proper funding and support.
It's probably not real. There are no reliable reports or evidence to support the existence of a 450-pound dog. Usually, dog weights are within a certain range, and this just seems way beyond the norm.
The unique relationships that can form in a dog pound make it interesting. The dogs might form friendships with each other, or a special bond with the people who take care of them.