Merit karma is a credit amount and demerit karma is a debit amount [owe the amount to repay]. One is free to spend his accumulated amount wherever he wants.

The Sikh gave him the money. When Menon asked for his address so that he could repay the man, the Sikh said that Menon owed the debt to any stranger who came to him in need, as long as he lived. The help came from a stranger and was to be repaid to a stranger.