Averages of HMI continuum light curves (normalized) within different threshold ranges. The threshold ranges are $3\sigma <(I_{\mathit{fm}}-\frac{1}{N}{\displaystyle \sum _{i=1}^N}{I}_{0i})<4\sigma$ (purple), $4\sigma <(I_{\mathit{fm}}-\frac{1}{N}{\displaystyle \sum _{i=1}^N}{I}_{0i})<5\sigma$ (sky blue), $5\sigma <(I_{\mathit{fm}}-\frac{1}{N}{\displaystyle \sum _{i=1}^N}{I}_{0i})<6\sigma$ (green), $(I_{\mathit{fm}}-\frac{1}{N}{\displaystyle \sum _{i=1}^N}{I}_{0i})\ge 6\sigma$ (pink). Here I_fm refers to the maximum value of all the WL emission pulses during the flare (see Figs. 2b1 and 2b2). I_0i refer to the values of WL emission pulses before and after the flare (also see Figs. 2b1 and 2b2). And σ is the corresponding standard deviation for I_0i.