Unable to find formulas

Hello Folks,

The attached Excel sheet containing a GANTT chart is a downloaded template from the Microsoft Excel Template section.

In this Excel sheet, I am trying to understand the design of it.

Question 01:

How the GANTT chart is coloured automatically based on the input of week numbers.

In the conditional formatting rules window, I see the formulas but I am unable to decrypt them. Could someone explain me?

For example, there is a formula saying, =PERCENTCOMPLETE.

Or, =PERCENTCOMPLETEBEYOND - How is the input being calculated and coloured?

Which CELL is being considered to validate the formula?

Gantt project planner_template.xlsx