Well Bill was saying the friction from rubbing the footballs caused an artificial increase in PSI. They would then make sure the balls were at 12.5 PSI in that state, or deliver to the refs and request they put the balls at 12.5 (plausible as Rodgers said the refs like to put balls closer to the low end of the spectrum). After the check, the balls PSI naturally lowers as it cools down from the rubbing. Then once they're out in the cold, wet weather, they drop even more. Whether the Patriots did all of this intentionally (likely) or unintentionally (unlikely), the science is accurate, and technically they did nothing against league rules.