Help Complicated formulae between columns

Hi

Thank you for your interest in my request.
I tried to apply your formula, but I dont find the good values, but it's close (weird), when i just apply the AVERAGE formula to the corresponding cells.
Im gonna try to figure that out.

I joined the sheet.

What is the "--" in the formula? (I know, I suck... But I better on R!)

Cheers,

B.