One boundary with two boundary conditions (Neumann and Dirichlet)

Please help me to understand about this issue.

I have a system of two PDE equations with two variables (u1, u2) need to be solved in General Form.

On a boundary 1, for example, I set up a Neumann boundary condition:
-n.Γ1 = f1
-n.Γ2 = f2

And then, still on the boundary 1, I set up one more Dirichlet boundary condition:
u1=f3 (Prescribed value of u1)
u2=f4 (Prescribed value of u2)

And I saw Comsol let me know that, the two conditions contribute together. So, which condition in two condition above will perform (affect to u2 on the boundary 1) in my model? (Both of them?)

Thank you so much for your help.

Best regards,