The lowest calcium level this test procedure could accurately measure was 15 parts per million (ppm). The water prior to adding the test samples measured 15 ppm. This represents a concentration of some value between "0" and "15" ppm. This is within the resolution of this particular test method. This value, know as the "bias" would be subtracted from the readings of the leachant water.
The conclusion is that no or very little (could not be measured) calcium leached from the treated samples. The calcium leaching test has been maintained for over two years. The 15 ppm remains unchanged.