The small-scale call back has been announced because those 53 units of the 2015 Mustang might've been fitted with sub-standard safety belt buckle assemblies. Engineers discovered that the assembly's belt buckle tension sensor may not have been calibrated adequately by the supplier.
Ford highlights that a buckle tension sensor that is not calibrated properly may result in misclassification of the front passenger seat occupant, which is classified as a noncompliance issue with Federal Motor Vehicle Safety Standard 208 "Occupant Crash Protection".
In worst case scenarios, the condition might lead to unsafe airbag deployment for the occupant, which could increase the risk of injury in a crash. Thankfully, the Blue Oval isn't aware of any accidents or injuries related to the mess-up.
So if you own a 2015 Ford Mustang assembled between August 18th to October 2nd, then contact your nearest dealer as soon as possible to find out if your 'Stang is due a visit to the service department.