The gravitational waves from the neutron star merger event GW170817 were accompanied by an unusually weak short gamma-ray burst (sGRB) 170817A. While association of sGRBs with mergers was predicted a long time ago, the luminosity of this prompt gamma-ray emission was weaker by a few orders of magnitude than all known previous sGRBs and it was softer than typical sGRBs. This raises the question whether the gamma-rays that we have seen were a regular sGRB viewed off-axis. We revisit this question by considering the compactness of this event. We generalize the compactness argument to an arbitrary viewing angle and apply it to GRB 170817A. We show our generalized argument can constrain not only the Lorentz factor but also the viewing angle for this event.