These are the values of the median distance (δM) for all networks to which the statistic applies and for which it was computed. In total, it has been computed for 1,315 networks.
The median distance (δM) is the median value of the distance between any two node pairs. This is calculated over each network's largest connected component, and takes into account pairs consisting of the same node, i.e., pairs of nodes of distance zero. Edge weighted and signs are ignored. Multiple edges and loops are irrelevant by definition for this statistic. The given values are never half-integers: Even when the median would be defined as the mean of two adjacent values, the value given is rounded up. This case is extremely unlikely in large networks.
The full definition of the median distance as well as its properties and relationships to other graph statistics can be found in the KONECT handbook.