That tank shape is called a flatback hexagon tank. The tank turned out GREAT!!!
I bought a used one in that shape and it was a LOT dirtier. Took me days of scraping, soaking with vinegar and scrubbing with salt to get it clean.
It was sold as a 33 gallon, but when I put the measurements in on a website, it came back a 40 gallon.
I was told because of the angles of the tank, it makes it look like there are more fish in it than their really are.
Hope you are enjoying your new tank.