https://www.bendix.com.au/bendix-new...-fluid-testing
"Bendix does not recommend using a conductivity tester as they have been known to fail when testing freshly opened brake fluid. Conductivity testers estimate the moisture content by converting the conductivity into an estimated boiling point.
Since brake fluids vary from formula to formula, this test is not an accurate result unless the tester is calibrated to the manufacturer’s product when new.
Bendix recommends a tester that heats the brake fluid to determine the correct boiling point. Using a boiling point tester is the only accurate way to test brake fluid performance."
Since you do not know what brake fluid your conductivity testers were calibrated to there is no way of knowing if the results you are getting are accurate.