Hello sir
I still have an outstanding  loan of $12 with you, and I will be needing a $500 loan to pay in 10 weeks but the $12 will ne deducted from my loan which implies that I will receive  $488 from you and expected to pay $500 plus agreed interest  in 10 weeks.
If its fine by you, then we can talk further about.
Thanks in anticipation for a favorable response from you.