The Compensatory Draft Pick system is not very well understood by anyone who hasn’t made a study out of it.
It’s a ‘secret’ system that the league owners administer for themselves.
However, through close observation over a number of years, certain people have created a set of rules that seem to explain how the system works and are able to project compensatory picks annually with great accuracy.
While OverTheCap didn’t figure out the rules, they have written extensively about the Compensatory Draft Pick system, and they publish a “Cancellation Chart” each season to help readers understand which teams are likely to receive compensatory picks.