The article says Male and female samples were matched 1-1, and a subset obtained by pairing up the best objectively job-appropriate male and female candidate

The article says Male and female samples were matched 1-1, and a subset obtained by pairing up the best objectively job-appropriate male and female candidates, with a margin-of-error of 2 years, in terms of experience in their field. Thus the dataset consists of 174,000 male and 174,000 female résumés. but that is assuming you are able to match two candidates objectively. Also "with a margin-of-error of 2 years, in terms of experience in their field" is a quite a margin for junior-mid positions.