Recently I noticed what I think are new icons/symbols located in the control center of my iPad Air 2. The symbols are located on the left side just above the volume control. They are in the form of 3/4 circles with the number 15 in the middle. I have googled and yahoo searched with no luck, other than seeing a few pictures that show what I see but not saying what is means. Can someone explain their meaning since clicking on them seems to do nothing. Thanks!