Understanding algorithim used for calcluting duration

I was trying to understand the algorithm used for calculating the total duration and how AW deal with overlapping period
can user manipulate the algorithm and set his own rules

this article is discussing the same overlapping problem, is this what AW implementation looks like

I am thinking of implementing a dashboard (with dash framework) using raw data provided from AW for my data analysis portfolio as a portfolio project for what is your advice, knowing that this is my first data analysis project