C++ :: Destructors Being Called More Than Expected?

In this code:

#pragma once
#include <iostream>
class CBox // Derived class {
public:
// Constructor
explicit CBox(double lv = 1.0, double wv = 1.0, double hv = 1.0) : m_Length(lv), m_Width(wv), m_Height(hv){}

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Before the program ends, at return 0;

I would expect the CBox destructor to be called 3 times but it is being called 6 times? Why? Also in this code:

#pragma once
#include <iostream>
class CBox // Derived class {
public:
// Constructor
explicit CBox(double lv = 1.0, double wv = 1.0, double hv = 1.0) : m_Length(lv), m_Width(wv), m_Height(hv){}

[Code] .....

Why is the destructor called 3 times? When have you really destroyed a CBox? Doesnt emplace only create it and store it, then thats it?

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For pushback:

void push_back(value_type&& _Val)
{// insert by moving into element at end
if (_Inside(_STD addressof(_Val)))
{// push back an element
size_type _Idx = _STD addressof(_Val) - this->_Myfirst;

[Code] .....