I don't believe this guy is 14% Sub-Saharan African. First off, the fraction doesn't even make sense (7/50) and second DNA testing comes in form of probabilities and with such a distant relation it wouldn't be a near-certainty of location. What likely happened here is the show who paid the DNA lab to test the sample pressured the lab into saying that there is a chance that he is at the most 14% Sub-Saharan, which they skewed into saying is a definite 14%.