Generally, to see the table or query behind a report, you can right-click
the report name and select Design View.  Once in Design View, you can select
Properties from the View menu to show the report properties.  On the Data
tab is the Record Source property.  If the Record Source is a query, you can
click in this field and then select the ellipsis (...) to view the fields
for the report, and make the necessary adjustments.

I want to change the "Units in Stock" field in the Product Summary Report.
I
can't seem to figure out where that field is or how it is calculated.  I
want
to take out subtracting "Shrinkage".  Thanks