Relationship of the area evolution phase and total unsigned flux evolution phase based on the SDD (top panel). Both of them are measured in percentage. Each gray point marks a sunspot group in one observation time. The linear fitted function is depicted with solid black line, its equation can be found in the upper left quadrant. Bottom panel: Umbral flux evolution phase as a function of time near the time of maximum flux measured in days for three sets of sunspot group sizes. The equations of the fitted regression lines and standard error values can be found in the bottom right quarter. The characters g and d mean the growth (negative values) and decay (positive values) phases of groups. The average growth and decay periods are calculated by using the equations of the fitted functions.