Problem with IsMdiContainer

I have 1 parent form (so to speak the menu) and a child form (employees form) using the property in the parent IsMdiContainer = true and coding in the tab used (click event) the following code:

        Ventana_empleados ir_a_emplead = new Ventana_empleados();
        ir_a_emplead.MdiParent = this;
        ir_a_emplead.Show(); 

It is assumed that with this code the child form should be shown inside the parent as follows:

--------- executing program ------------------

------- opting tab employees ---------------

As you can see the child form (employees) is completely mismatched from its dimensions, nor maximizing the tab is able to adjust proportionally to the parent form.

------------------- child form (employees) with original dimensions -------

What am I doing wrong? because the dimensions of each element of my child form are mismatched when I run the program.