Java Unit Testing JaCoCo

Question

I am new to Java and JaCoCo. I have a simple interface and an implementation as below.

public interface Action<T>{ T getT(T in); }
public class Foo{...}
public class ActionImpl implements Action<Foo>{ public Foo getT(Foo in);}

The class ActionImpl only has a default constructor. On writing unit tests for the class ActionImpl, JaCoCo reports 100% coverage for the ActionImpl but reports 88% coverage for ActionImpl.new Object(){...}.

How do I interpret this report and where does ActionImpl.new Object(){...} come from?