A300
Flight Crew Air Transport Pilot (ATP)
Situational Awareness; Communication Breakdown
Deviation / Discrepancy - Procedural Published Material / Policy
General None Reported / Taken
Procedure; Human Factors
Aircraft blocked out 1 minute early.  We had received a revised release time during preflight checks.  I had calculated the 15 minutes.  At [one minute before the release time] I called for pushback clearance with Ops; at the same time the Captain misunderstood what I was doing and told the ground crew we were ready to push back.
A300 First Officer reported pushing back early due to miscommunication between the flight crew.