I test every new bucket of salt no matter what brand. I find each bucket varies quite a lot. Actually, to take a bit of salt out of your wounds, my newest bucket of IO only has 1180 ppm Mg. I'm going to mix up the bucket real good tomorrow, and try testing it again because I haven't had a bucket that low before. The Calcium is testing high at 400 ppm too, so that's weird because IO is usually 360-370. Or maybe I've been away from my tanks too long over winter and I forgot how to test!!!
