I took their projected cap leading into the off season and then built a formula looking at their impending free agents and developed a score. That score is basically to show how easy it will be too keep that team together heading into future seasons. The Bears for instance are showing a negative projection after season one, but also have some decently well rated guys to resign.
To be fair it doesn't account for potential retirements/cuts/ or simply not wanting a high rated guy back. I was doing the best with what I had to work with. I actually had to go import salaries from a 3rd party then cross my sheets over.