If that's the reading at 2ft away from the center of the light, while the light is at 24", its accurate. I am guessing, however, that you're measuring from the center. At 24", the center should read around 700.
Your light is also dimmable, there's a hole in the top of the drivers. Get a screwdriver in there and test the dimmable function to make sure it's running at 100%. Mars Hydro lists all of their PAR readings on amazon, so look up your light on amazon to get the charts to compare your readings to. Best of luck friend!