I purchased an HDD Air last week which I love. I calibrated the battery like I was told on the forum. Today I turned on my fully charged Air at my gf's house. In ten minutes of use with wifi off and the screen at its dimmest, I am at 93%. Istat shows that I had about 2:00 remaining, now it is at 3:34, it went up? What's the deal? I was concerned also because I felt like my battery went down quickly. In ten minutes of use I was at was 93% and was only doing word processing. As I typed this, it changed to 4:14. Have any of you had issues? Is this common?