For polylines and polygons, the app zooms to the extent of the feature.
For points, there is a "pointZoomScale" property that can be added/modified in the dashboard json (via AGO Assistant or other) to set a specific zoom scale. This property is not exposed to the dashboard creator at this time and must be manually changed in the json.
The app currently defaults to 10,000. So setting this property to a value like 1,000 will allow the map to zoom in more. The setting is per-webmap.