In StoryTeller charts and tables, series with low base size can either be hidden or shown with a warning. A system logic is used where hidden series are shown with ** and series with low base size (are still shown) with a *.
To increase flexibility there is an option which makes it possible to customize the characters shown in charts/tables when the base size is too low. The option is a setting on a project level and it’s placed on the general Project settings page, as shown in the image further down. 

Below, the left chart uses the default visualisation (*), and the right chart uses the new settings.

The following image shows where to find these settings on the general Project selection page