Is the public class object in scripts only a reference of the game object's component?

I am new to both unity3D and C#. After creating my first "Hello world" program, I have a question about the public class object in script. In the level, I have two game objects (A & B). There are two scripts attached to these objects separately. The script A is as follows:

 public class ScriptA : MonoBehaviour
 {
 
     public int m_value1;
     public int m_value2;
     public int m_value3;
 
     // Use this for initialization
     void Start()
     {
         m_value1 = 0;
         m_value2 = 0;
         m_value3 = 0;
     }
 }

and the script B is:

 public class ScriptB : MonoBehaviour {
     public ScriptA m_objectA;
     public int m_value1 = 0;
     public int m_value2 = 0;
 }

I am now wondering that whether the m_objectA in scriptB only a reference of object A or the data of object A is stored in two places in my memory. I am really worried about this problem especially when I want to use object A to store enormous data. Thanks a lot!