I am trying to put a total column in dataview

What I’m trying to do

I have a repository of movies in which I discriminate by seen and not seen and I want to add a Total column to know the time I have invested in watching all the movies and for this I am using dataview this is the query I have at present

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Things I have tried

I have tried basically what you see in the picture above but I really don’t know much about it, I would appreciate any help.