How to get aggregate values from insight reporting?

I have two CDO tables( Table X, Table Y ) which has been enabled with Insight reporting-

both tables has got a field as "Brand" - Sample is as shown below

Brand Names Table X Table Y

Brand A 1 N/A

Brand B 4 N/A

Brand C 2 3 ( here 1 contact is present in both tables )

Brand D N/A 2

Brand E N/A 1

When i prepare an analysis in Oracle Eloqua insights -

adding both Brand fields in two tables - & add total contacts metrics field-

i dont get proper count details.( the result is depicted as below)

Brand Names Total Contacts