When comparing Item Counts from the Email Sender Domain and Email Recipients Domain in Project Explore 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 (ex. Doc, Txt, xls, pdf).
Now you matches should come close. If they are still off slightly, there maybe additional items in the BCC or CC column.