Use the result of the numbers column (the sum)

Hi everyone,
Was wondering if the sum that comes out at the end of the number column can be used?
I’m trynig to set up a board that analyses cost and revenues to get the redditivity out of it (revenues-cost).
Can anyone help me?
Because you cant set negative numbers for a fixed group and also in the dashboard you can only sum the elements and not like see the difference between two groups.
Thanks everyone who stops by