How to understand what is required in this task

I am working on a task but I can not understand this part of it:

Define a delegate bool GreaterOf(Comparable obj1, Comparable obj2) (obj1 is greater than obj2) to compare Comparable objects in terms of SizeOf(); For each of the structs Point, Vector and Triangle define a private method GetSizeOf(Comparable obj1, Comparable obj2) to implement the delegate GreaterOf for the respective struct. Define a property to get the instance of GreaterOf for GetSizeOf().

Here, Comparable is an interface that has that method declaration:

double SizeOf();

I have three structs that implement it(Point, Vector, Triangle). In each of these structs I have defined the method GetSizeOf as follows:

For the Point struct:

private bool GetSizeOf (Point obj1, Point obj2)
    {
        return obj1.SizeOf() > obj2.SizeOf();
    }

What I don't understand is this: Define a property to get the instance of GreaterOf for GetSizeOf().

EDIT: If this would help, further on this is what it is in the condition:

Define a BubbleSort( Comparable[], GreaterOf g) method to sort an array of Comparable objects, where the delegate GreaterOf determines the ordering sequence (Assume the elements of Comparable[] are all Points, Vectors or Triangles only)