Problem with weak form-SBC

Hello to everyone,
I am new to Comsol (i use the3.5a version) and i try to implement an SBC using the weak formulation in a simple structure in order to learn the weak form.Perhaps I have not understood it enough.
My first try was to use the rf-formulation of the SBC, then multiply with the test function and put it in the weak tab in the boundary setttings.
Is this a wrong way?

Thanks in advance