Calculate Average performance score for the Talent Review meeting

Summary:

Hello,

We have a requirement to display the average performance score to managers during the Talent review preparation process.
There are two performance documents for the year: 1 for the first semester and 1 for the second semester.
For an employee that got a rating of:
- 3-Medium for Semester 1
- 5-Outstanding for Semester 2.

We want the performance score displayed during the talent review preparation process to be 4-Excellent which is the average.
Currently, only the last score is displayed.

Please, how can we achieve this?

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