Yep. Specifically how many times they tested the ball on their own sidelines. I've read that as much as 0.25 psi can leak out when a needle is inserted/removed, if the equip manager tested it, then re-tested to show Grigson, then re-tested to show Kensil, all of a sudden down by 1 psi is down by 1.75 psi.
This isn't rocket science. If the other balls were tested and shown to be 'just a tick' under, or even under by 1 psi, the atmospheric conditions 100% exonerate the Patriots, and the lone 2-psi-under ball was retested at least once and perhaps multiple times, skewing the data.