Time interval. Interpretation of this time interval depends on the context
in which it is used. E.g. for synchronization thresholds the interval of 1 hour
usually means "number of changes in one hour interval". For dashboards it may
mean "number of errors in last hour" and so on.
If there is a danger that the interval might be misinterpreted then the
precise interpretation may be specified by using additional items in this
data structure.