Compare-Object show mathmatical difference

Trying to compare two excel sheets, select out a specific column and then compare the values in each row and return the difference.

I removed the side indicators cause it was throwing off my format in the post.

$Diff = import-csv C:\scripts\Testing_diff.csv | Select-Object Name, Volume
$reff = import-csv C:\scripts\Testing_reff.csv | Select-Object Name, Volume
Compare-Object $reff $Diff -Property Name, Volume -PassThru -IncludeEqual

and it just spits back the following, Trying to get it to give me back the difference of the volume data.

Name                  Volume   SideIndicator
----                  ------   -------------
Development_b_001     1549.50G           
Production_b_001      11.57T              
Production_b_002      1600.03G            
Development_b_001     549.50G            
Production_b_001      1.57T              
Production_b_002      600.03G 

Compare-Object will not calculate for you. It compares objects or object properties and tell if it’s equal or not. If you need to calculate a difference you will have to do it by yourself.