Sum duration columns

Hello friends : D I hope y’all doing well

So, this time I have a new challenge and I reach the point where I need another point of view, or an advice.

I have a table that looks like this:

d1 - - - - - - d1Duration - d2 - - - - - - - d2Duration

And after some attempts to sort and sum all this durations I got:

d1 - - - - - - d1Duration - d2 - - - - d2Duration - Duration output

My expected output is the sum of the values, but instead this method is substracting.

I´ll appreciate any idea : D

-N