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The Alessandrini A$+$ indicator is a quantitative measure of star clusterdynamical evolution based on the mass-segregation of blue straggler stars. A$+$is defined as the integral of the cumulative distribution of blue stragglerstars with the radius measured in logarithmic scale, minus a term related tothe reference population used. In a companion paper I introduced a simplifiedmodel of dynamical friction and calculated the A$+$ indicator analytically.Here I show further properties of the time evolution of A$+$, focusing inparticular on the physical interpretation of its time derivative $d{A^+}/dt$. Ifind that $d{A^+}/dt$ is the mean of the reciprocal dyamical frictiontimescale, weighted by the density of blue straggler stars. I show that it isnon-negative (as expected based on monotonicity) due to the density ofblue-straggler stars being non-negative and that, for a dynamical frictiontimescale that is non-decreasing with radius, $d{A^+}/dt$ is alsonon-decreasing with time, making the A$+$ indicator a convex function.

Further properties of the dynamical clock A+ indicator in a toy model of pure dynamical friction