I have a pivot table & I'm trying to get a difference from two columns within the pivot table.

This is a screen shot of pivot table.

[Imgur](https://i.imgur.com/iUyA5F2.png)

This is a screen shot of the fields selected.

[Imgur](https://i.imgur.com/wjl25eZ.png)


I've tried adding a calculated field but not getting anything.