In EPDM 2008, what is and what is the purpose of the show/hide configuration option found in the Contains and/or Where Used tab?

Is there a reference topic for this found in the HELP menu?

Additionally,  referencing the attached images - when the 'show' configurations is on the resulting Contain Tab info does not include one file.  When the 'hide' configurations is selected (greyed out), the Contains Tab info includes the highlighted one.

Why the difference?

Please note that the reason for these question is that formerly both the 'show' and 'hide' would display the same info regardless of which was selected.  By default the 'show' is on/highlighted.  Recently, around first of year, this started functioing as shown with not all info displayed in the 'show' causing you to toggle to the 'hide'.  It appears 'hide' is displaying all correct in however this is not the default.  Is there a way to make the default be the 'hide' option?

Thanks for your help and insight.

Tim...