The age ranges here are appoximate.
Sometimes authors are specific; sometimes they are not!
(And sometimes the author has a mix of characters with specifed ages and characters without.)
We expect these search criteria to be of most use where you have actors in a specific age range for whom you want to find roles.
If you select one or more age ranges (to match the playing ages of your actors), the search will find plays containing characters of those ages and characters with unspecified ages.  Usually, the characters of unspecified ages will also be playable by actors of the specified ages.
(Occasionally there will be anomalies where the author has not specified ages, but, for example one character of unspecified age is the parent of another character of unspecified age.)
These are playing ages - actors of different ages might be suitable for the roles.