What an absolutely HORRIBLE background in the tank LOL!
Like most things on Craigslist, I'm sure the seller is open to negotiation, especially if you bring a tape measure and show them you know how to accurately calculate the correct size.
If you think that's big, there was a 1,000 gallon posted in New York State that I saw posted in a thread on Monster Fish Keepers. That thing was literally the size of a swimming pool!