About Dashboards : Overriding view scope
  
Overriding view scope
Panels will by default use the relevant scope objects applied to the view. For example, a Metric Chart panel configured to display CPU utilization would consider the view’s device objects to be relevant scope objects.
Panel scope can be overridden in the panel’s editor to only consider a subset of the overall view scope.
Overriding view scope
Not all panels support multiple scope objects. A specific scope should be configured for these panels, otherwise it will use first scope object applied to the view.
Specific scope warning