Macbook air , Sudden 4% Battery drop down ! I have recently bought my macbook air 13" 256GB from canada apple store ,I have full charged it 2 times in 100% , and both times after i unplugged my macbook from the power ,the buttery sudden dropped from 100% to 96% in a second!!!! whats the problem? is that normal ? this is my first Mac ! I have confiused please let me know if this is a problem , i will go to app store and ask for exchange !!