Increase of the flux with respect to the underlying continuum vs. temporal variability for the sample of late flares (blue squares) compared with the early flare sample (red stars). The black stars and square correspond to the SGRB early-time and late-time flares, respectively. The solid lines limit the kinematically allowed regions for density fluctuations on-axis (blue line) and off-axis (red line), for off-axis multiple regions density fluctuations (green line), for patchy shell model (black line) and for refreshed shocks (pink line), see Ioka et al. (2005) for details.