Using our example from the first section where we selected  Modality for the Vertical Axis and Gender for the Horizontal Axis, we now add the default logic from this section of the form.  The combination will yield the table shown below.  Notice how the  displayed Gender values include "UNK" or Unknown values.

This occurs because Gender was not used as criteria for this query example.  The query simply called for prevalent patients for 2000, regardless of any other criteria.  Thus, the data returned includes ALL records matching that criteria.