Where MyUltimateClass inherits from both the first classes, right ?
Your definition is correct, but your example is incorrect. In your example, MyUltimateClass does NOT inherit from both the other classes. It only inherits fom MyDerivedClass. To you and I, it inherits from both, because it has the contents of both, but to the compiler, it only inherits from MyDerivedClass. The compiler doesn't care that MyDerivedClass is derived too, all it has to do is is keep track of one superclass for this class.
Multiple inheritance would be where you had a class called car, a class called boat and a class called amphibious-vehicle which inherits from both, though car and boat are unrelated.