Thats better, but, watch that pH close now, just in case. That alkalinity is still low if that test method is working and the reagents are good. The rest are great now. The sand you are using wouldn't boost the Mg too much, I don't think. Should help keep things just right actually. Some of our test kits for aquarium use are as much as 25 to 30% in error. In other words a true calcium of 525 may return a test value of 410 with an aquarium test kit. After all, when is the last time anyone ran a control on any kit other than a pH meter? Truthfully though, those numbers look like a balanced system with an alkalinity test kit that is a little off.