These are the values of the mean distance (δm) for all networks to which the statistic applies and for which it was computed. In total, it has been computed for 1,325 networks.
The mean distance (δm) equals the average distance between any two nodes, where the distance is defined as the number of edges in the shortest path between the two nodes. Same-node pairs are included in the calculation. Only the network's largest connected component is considered.
The full definition of the mean distance as well as its properties and relationships to other graph statistics can be found in the KONECT handbook.