Social charges on "Autres revenus du foyer fiscal" added to auto-entrepreneur income

I will be starting an auto-entrepreneur business from September 2015 under trading of goods category (Regime BIC, RSI Vente, Commercant). While the expected turnover will be 50,000 euros, well within the turnover limit. I will also be receiving 20,000 euros annually as other income (investment income from overseas). I have run the calculatrice and it shows no change in my income tax and social charge liability for having added the 20,000 euros as Autres revenus du foyer fiscal (net imposable). Is this correct? I will have no social charge and income tax levied for this additional income?