As of September 7, Overthecap.com shows that the Packers have $6.803 million in salary cap space. Sportrac.com lists the Packers with $2.979 million, which ranks 31st out of the 32 NFL teams. The difference between the two estimates is very close to the $3.78 million, which I have suggested should be associated with the grievance over Martellus Bennett's signing bonus.
After digging a little further, I learned that since the Packers filed the grievance in 2017, any award issued in 2018 counts toward the team's 2018 salary cap. If the Packers lose the appeal, OTC will deduct $3.