These are the values of the reciprocity (y) for all networks to which the statistic applies and for which it was computed. In total, it has been computed for 324 networks.
In directed networks, the reciprocity (y) equals the proportion of edges for which a reciprocal edge exists, i.e., for which another directed edge connects the two connected nodes in opposite direction.
The full definition of the reciprocity as well as its properties and relationships to other graph statistics can be found in the KONECT handbook.