Help to read program code

I might be beginner who tries too hard thing. But I want to read real program code. I provide link to it.
That is chemistry command line program it takes two files as input and calculates third as output.
Or if you set --score_only it becomes simpler and provides one number only output.
That number is here:
Main.cpp:166
 
log << "Affinity: " << std::fixed << std::setprecision(5) << e << " (kcal/mol)";

Full code here:
 
  https://github.com/ProzacR/vina 


What I want is basically formula how that e is calculated.
At first I though that it will be simple, but in code functions call functions and thats seems bit too hard for me. I spend ~2 workdays trying to learn more C++ and get it and still can not find it. If is called 'scoring function' and there is coring_function.h file but it contains no mathematical operators at all.... likely formula is distributed over few functions in bit complex way.

Can someone find me those lines with e calculation formula?
Bit thanks is someone can do this. ;)
I suppose "e" here is not a base of natural logarithm...
If nobody helps you by tomorrow mornong which will be in 9 hours in my current timezone I will look into it.
Github link does not work
Strange... try this one:
https://github.com/Ashod/vina
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