根据说明书：The residual is an indication of how well the calculated data was fitted to the measurement data. A good fit is indicated by a residual of under 1%. A residual of over 1% may indicate use of incorrect refractive index and absorption values for the sample and dispersant.
其实就是理论光强和实际光强信号的差异，一般小于3%，良好匹配小于1%，不过不是绝对的。通常粒径小，残差相应会大些。