My J-370 is essentially the same size as your newer model. Mine holds right around 500 gallons. However, the actual volume is far less important than you may think. As others have pointed out, you will likely NEVER measure your chemicals based on the volume. And chemical usage in these things can (and should) be MUCH MUCH more simple than some think. I initially used di-chlor and the minerals but quickly learned that with the CD ozone, the only thing that was needed is a couple of TABLESPOONS of di-chlor after each soak. For the first 3 or 4 years, I would soak 2 to 3 times a week and this routine was more than enough. In the past year or so, I have backed down to once a week and sometimes only once every 2 weeks. Guess what, the same EXACT ritual is also sufficient for those periods as well (a couple of tablespoons a week is MORE then enough to maintain good water condition).
What happens when done this way is that the chlorine is consumed and each soak is basically in clean, clear water with no chemical smell.
