Final results for mean negatively charged pion multiplicities $\langle \pi^{-} \rangle$ from Ar+Sc collisions are the main topic of the talk. The data was taken recently by the NA61/SHINE collaboration for a wide range of momenta - 13, 19, 30, 40, 75 and 150 \textit{A} GeV/c. Starting with rapidity distribution of differential spectra $\frac{dn}{dy}$ extrapolated to unmeasured regions, the procedure of obtaining the final multiplicities is presented. A new scheme to calculate the mean number of wounded nucleons $\langle W \rangle$ utilizing the EPOS MC model is described. Using data from other experiments, a comparison of $\frac{\langle \pi \rangle}{\langle W \rangle}$ for different collisions and momenta is discussed.