These are the values of the in/outdegree correlation (ρ±) for all networks to which the statistic applies and for which it was computed. In total, it has been computed for 268 networks.
In directed networks, the in/outdegree correlation (ρ±) is defined as the Pearson correlation coefficient between the indegree and outdegree of nodes, measured over the total set of nodes.
The full definition of the in/outdegree correlation as well as its properties and relationships to other graph statistics can be found in the KONECT handbook.