Law of chemical equivalence
This Reaction is a Disproportionation Reaction, that is, a reaction involving both oxidation and reduction of a single species, in this case : Iodine. This is not one reaction but a combination of two reactions:
$$\ce{KIO3 -&gt; I2}$$
And
$$\ce{KI -&gt; I2}$$
Therefore, by applying law of chemical equivalence in both reactions and adding the equations :

$m_{eq}$ of $\ce{I_2}$ (from both reactions) = $m_{eq}$ of $\ce{I_2}$ (from $\ce{KIO3}$) + $m_{eq}$ of $\ce{I_2}$ (from $\ce{KI}$)