Football is a chess match. Often times that goes well beyond the field of play. One area teams can try and gain a competitive advantage is via the compensatory pick formula.
For instance, the New England Patriots have been playing the system for a while, ensuring they signed few players who counted in the formula than they lost. Thus with the Raiders employing a staff and front office made up of a lot of former Patriots, they are now projected to receive three comp picks in next years’ draft.
Part of the rules surrounding which free agents qualify for compensatory picks involves timing.