How to create a Fast Formula for performance calculation?

Summary:

How to average 2 overall section score through Fast Formula?

Content (please ensure you mask any confidential information):

We have a performance document divided in 2 sections (personal goals and group goals).

One section has a weighted summary that gives the overall score of the evaluation.

The other one cannot be changed by the manager and it is populated through an HDL. Since as far as we know it doesn't exist the possibility to upload every single goal score through HDL we are ok with loading just the overall score of the section (through HDL).

Problem is that by doing so the default Overall Summary of the page cannot properly average the 2 overall scores (it seems that it averages single goal scores that don't exists in the second case).