Hi guys, I just purchased my 13" rMBP (the mid-range 256GB one) yesterday. After a first full charge, at 100% battery remaining, the estimated time remaining shows to be 7:10??? There is no app open, nothing is running. Why is the battery life under 8 hours? I thought the 13" is supposed to have 9 hours? I got a low-end 13" before I exchanged it for this one, the previous one had more than 10 hours after a full charge. Is this an issue?? Should I bring it back to Apple?