  We consider the infrared (IR) limit of the nonlinear integral equations
(NLIEs) for the boundary supersymmetric sine-Gordon (BSSG) model, previously
obtained from the NLIEs for the inhomogeneous open spin-1 XXZ quantum spin
chain with general integrable boundary terms, for values of the boundary
parameters which satisfy a certain constraint. In particular, we compute the
boundary S matrix and determine the "lattice - IR" relation for the BSSG
parameters.
