An electric field $$\vec{E} = 4x\hat{i} - (y^2 + 1)\hat{j}$$ N/C passes through the box shown in figure. The flux of the electric field through surfaces ABCD and BCGF are marked as $$\phi_I$$ and $$\phi_{II}$$ respectively. The difference between $$(\phi_I - \phi_{II})$$ is (in Nm$$^2$$/C) ___________.