I have a tf 100 test kit. A chlorine discrepency always exists between the Method using R-0870 / R-0871 and the R-0600 test. Tonight I tested using the R-0600 and it showed my free chlorine as being well over 5 ppm. By drop 2, the color was darker than the 5 PPM color on the scale. I did not dilute and see exactly what it was because I knew the number was impossible. Last night I tested with the 870 /871 and had 4 ppm chlorine and no combined Chlorine. No Chlorine was added to the pool and the Basic test showed way over 5. I tested again using the 870/871 and my F.C. was 2 and again I had no combined chlorine. Am I doing something wrong, or is there something interfering with one of the tests?