Adding a rankings - set column - relations

I want to set a column based on a position entered against the items on the list in the app. The complication is that I’ve used a Relation between sheets and the positions are in the sub-relation.

The first sheet is Day>Ring>Class
The second sheet is Class>Competitor Number>Competitor Name> Position (I want to update the positions of the list of competitors - scoring them)

It’s sometimes hundreds of classes and the number of competitors varies per class.

Any suggestions on how this can be done?

Thank you