One teaspoon (about 6 grams) of sodium bicarbonate (NaHCO3) per 50 liters/13.21 gallons of water will increase KH by 4 degrees and will not increase general hardness. Two teaspoons (about 4 grams) of calcium carbonate (CaCO3) per 50 liters/13.21 gallons of water will increase both KH and GH by 4 degrees.
He then asked me, how can one teaspoon be 6 grams yet two teaspoons be 4 grams in this passage? I think the answer is obvious. Can you get it?