Manganese VI has ability to disproportionate in acidic solution. The difference in oxidation states of two…

In acidic solution Mn(VI) become unstable relative to Mn(VII) and Mn(IV)

$3{\mathrm{MnO}}_4^{2-}+4{\mathrm{H}}^{+}\to 2{\mathrm{MnO}}_4^{-}+{\mathrm{MnO}}_2+2{\mathrm{H}}_2\mathrm{O}$
So difference in oxidation state of product ions of Mn is = 3