I finally got my Ipod touch today, it was only 50% of battery left so i charged it after using it for awhile. When i charged it the battery was down to about 15% , i have had it plugged in now 3 hours and i am confused about something. When my ipod 4 was fully charged the icon up top went from a lightning bolt to a plug, but after 3 hours i still see a lightning bolt up top near the battery indicator. Is there a problem or is this the way it is for this version??