When comparing Item Counts from the "Email Senders Domain" and "Email Recipients Domain" facets in Project Explorer to what is found in the quick search using (From con gmail) or (To con gmail), the counts do not match.
In the column grid view, click on the extension facet and uncheck all the extensions that are listed in there (e.g. Doc, Txt, xls, pdf).
Now your matches should come close. If they are still off slightly, there may be additional items in the BCC or CC column.