This is an overlap. Two items have been plotted in the same place. *1 is the first overlap. If there are others they will be labelled as *2, *3 and so on.
In this example there are four risks plotted but we can only see labels B, C and *1. The overlap is the plot of risks A and D and is shown as *1 - see the area in the red square.
The overlap legend list all plots in each overlap.
To display the overlap, click Hide/Show and then Overlap legend.
