Having trouble styling custom UI

I want to make a two-column UI in unity to manage a pair of fields so I made a custom UI. Howerver, I came up with this inconvenient view and can't help myself. This is what it looks like.



My trouble is: I can't remove the "Element" tag. Is there a way to remove them?
Besides, I'd like to know how to add a little space between these two columns.

This is my code in my custom editor(I did't use property drawer for it didn't seem to work):

Code (CSharp):

1.  
2. public override void OnInspectorGUI()
3.         {
4.             serializedObject.Update();
5.             EditorGUILayout.PropertyField(_itemNumber);
6.             _itemNumberToShow = _itemNumber.intValue;
7.             GUILayout.BeginHorizontal();
8.             GUILayout.BeginVertical();
9.             GUILayout.Label("Item Name");
10.             for (int i=0; i<_itemNumberToShow; i++)
11.             {
12.                 SerializedProperty itemProperty = _items.GetArrayElementAtIndex(i);
13.                 EditorGUILayout.PropertyField(itemProperty);
14.             }
15.             GUILayout.EndVertical();
16.             GUILayout.BeginVertical();
17.             GUILayout.Label("Drop Chance");
18.             for(int i=0; i<_itemNumberToShow; i++)
19.             {
20.                 SerializedProperty chanceProperty = _chances.GetArrayElementAtIndex(i);
21.                 if (chanceProperty.floatValue < 0)
22.                     chanceProperty.floatValue = 0;
23.                 EditorGUILayout.PropertyField(chanceProperty);
24.             }
25.             GUILayout.EndVertical();
26.             GUILayout.EndHorizontal();
27.             if (_itemNumber.intValue < 0)
28.                 _itemNumber.intValue = 0;
29.             serializedObject.ApplyModifiedProperties();
30.         }
31.  

Thank you for reading!