File size discrepancy in Search Term Hit Report

Problem:

I have a search term hit report with a total family size of 20 GB. One of the search term has the family size of 10 GB. I removed the search term whose family size is 10 GB. Now I expect the report to show the total family size to be 20-10 i.e. 10 GB. However, the report is still showing me 20 GB.

Resolution:

The total family file size at the bottom of the report is not the sum of the above family file sizes .

Let us say suppose we are searching for 2 terms ( A and B) the both hits the same file whose size is 10 GB.

So now the report would look like 

Term                                           direct size             Family size 
A                                                 10GB                     10GB
B                                                 10GB                    10GB
==========================================
Total doc hits                              10 GB                    10 GB