From the article (and the company themselves): "The company said it approaches the development of its tools and reports with scientific rigour, but admits its

From the article (and the company themselves): "The company said it approaches the development of its tools and reports with scientific rigour, but admits its results are "statistical estimates." It is very likely that there's a fine print on their procedure that everything is a Guesstimate and while their algorithms will process things the same for every sample, there's just too much variations that are unaccounted for even in such controlled environments. What would surprise me for example is if someone sent in their DNA for analysis twice on the same company and get varying results. That would mean that the process itself is not well-established.