In a reaction ${\mathrm{MnO}}_4$ is changed to ${\mathrm{MnO}}_2$ • The change in oxidation state of $\mathrm{Mn}$ is

Here In a reaction ${\mathrm{MnO}}_4$ is changed to ${\mathrm{MnO}}_2$ • The oxidation number of Mn is +7. When it  changed to ${\mathrm{MnO}}_2$, the change in oxidation state of $\mathrm{Mn}$ is -3.