Fast Formula for calculating Overall Rating in Performance Document

If anyone could share the sample of fast formulas they have written to calculate ratings, that would be really helpful as there are not many examples out there for these.

I am trying to write fast formula to calculate the overall rating based on two different section ratings:

1) Trying to find out DBIs that would correspond to those section ratings(both are manual ratings, section type for both are 'Profile Content')

2) Trying to understand how can I differentiate between these two sections in the fast formulas as they both are of same type

Any pointer/sample will really be helpful