You use this key figure together with the Reconnection Date as Key Figure key figure in order to calculate the duration of the disconnection in the query.

For this purpose, the Disconnection Date characteristic is copied to this key figure.

You do not have to display the key figure in the query drilldown. It is only used in the calculated key figures.

Time characteristics are generally converted to key figures because you cannot calculate differences with characteristics. However it is possible with key figures.