I got a new pair of 42 mm genuine Apple Sport Band. I notice that I there is a very shallow dimple or depression around the buckle mechanism on sport band. It is very barely noticeable but can be felt if you run your finger over the surface. It is perfectly circular so I don't think it is a manufacturing defect. It is very difficult to capture it on camera, but I circled the area on the band to denote where it is located: I don't own a sport band previously, so I can't make any comparison. Anyone can solve this mystery? What is it for?