To clarify for the op a bit further.
For each mol of reaction there is a net change of moles of 1/3. For instance, if 4 moles of sulfur dioxide were to react with 2 mols of oxygen gas, then 4 moles sulfur trioxide would have been formed. The net change in moles is 4-6=-2, that's a loss of 2 mols for every 6 moles of gas which undergoes the reaction.
Thus .00812, if your calculations are correct, represents the net change in moles. You would need to multiply this quanty by 3, to get the total moles of gas which underwent the reaction, than multiply by 4/6, overall multiplication factor is 2