So that you can be 100% confident in the accuracy of your test results, every test participant is processed twice using completely different machines and personnel for each test. A forensic scientist then compares the results to assure that the test was performed correctly. There is no extra charge for this service.
Laboratories do not often make mistakes. 2x double-blind testing is designed to catch those rare instances when something has gone wrong so that you will have complete confidence in the results of your DNA Paternity Test.