Can't get parent repeating group single item without getting everything

Basically, when I’m trying to do some math nested a little further down in my repeating groups and I try to back up and get a returned ID or something from an api in a higher repeating group, it returns the whole list of items intead of just the one thing I want.

The only way I’ve found around this is to do the math directly on the api calls, but now that means I have duplicate api calls, over and over and over every single time I calculate a value, which makes it slow as heck.

Thoughts? Maybe I just don’t understand the structure well enough. Here’s an example.

And this is my main app