What is the equivalent mass of ${\mathrm{S}}_2{\mathrm{O}}_3^{2-}$ as per the following disproportionation reaction

${\mathrm{S}}_2{\mathrm{O}}_3^{2-}⟶{\mathrm{S}}_4{\mathrm{O}}_6^{2-}+{\mathrm{S}}_2^{2-}$

where the charge above species represents charge on the ion and not oxidation state?