Each line of numbers represents a haplotype for a participant in the study. Each number represents an STR marker, which is taken from the junk DNA on the y-chromosome.
Different haplotypes have different lengths because participants have decided to participate at different levels. Family Tree DNA, the official testing company for this project, provides standard 12, 25, 37 and 67 marker tests. Participants will have different numbers of markers only if they tested with a different company or bought additional markers a la carte from Family Tree DNA.
Haplotypes are sorted by haplogroup and group. Those grouped together appear to be related, although because of the large number of 12-marker haplotypes, in some cases, it is impossible to be certain. In general, if a pair matched on 11/12 or more and had the same surname, I tentatively placed them in the same group. With larger number of markers, it was possible to be more certain.