If you log into your Self-Serve portal, navigate to "Payment" and then "Transaction History", and then pick a suitably large time range (e.g. "Last 6 months") and then click "Search", you'll likely see your initial credit/payment, followed by "$10 Referral Credit/Crédit de recommandation de 10 $" (note that this is in descending chronological order, so you'll most likely see it at the top of the list once applied). As others have stated, this could take a few days. In my experience, it showed up on the day following initial activation (i.e. within 24 hours in my case).
