By using the keypad and label you are trying to mimic some historical equipment like a cash machine, or something like that. Don't do it. I can only confuse the users and drive them mad. The popular idea of mocking old bad machines using modern computer is counter productive. All data should be presented in a natural way and exactly in the place it its typed in, nowhere else. There should not be a label and, especially, no keypad.
Use, for example, this control:
https://wpftoolkit.codeplex.com/wikipage?title=MaskedTextBox[
^].
—SA