Your Calcium Hardness may be around 350 since it's smaller than Total Hardness which also includes the hardness from Magnesium. The actual ratio of Calcium and Magnesium varies by type of water source -- the factor of dividing by 1.4 that I used is based on a Calcium to Magnesium ratio of 4 to 1 (the hardness readings are in ppm calcium carbonate equivalent while the ratio is based on ppm of the ions themselves). In some areas where I live, the ratio is closer to 2.6 to 1 so the factor to get Calcium Hardness is 1.6 which would mean in your case something closer to 300 ppm.

The bottom line is that your CH is probably not far from where it should be.

Richard