Got a brand new macbook air 2013 13" i7/8GB Was looking forward to the 12 hour battery life yet mine shows 6 hours and 40 min after a full charge. Display is at 75-80% of full capacity. Is my battery defect and do I need to send this back to Apple so they can fix it? I bought this machine in thailand via the online apple store. In thailand there is no 'no questions asked refund rule' if under 14 days after purchase, but obv I do have a warranty. Or is this something I can fix myself? Does the battery need to be reset or calibrated or something?