📈 Track project progress in a Portfolio based on weight, effort or number-based goal (not just % of task completion)

I have added a field in my project which is supposed to display the weight of each task.

But when I try to create a roll up in portfolio to add up the fields from the projects, the field doesn’t show up as an option.

How can I get the data from my project and add it up in my portfolio? Am I missing a step?