The Story of the Jinns listening to the Qur'an

Imam Ahmad recorded from Az-Zubayr that he commented on the Ayah;

وَإِذْ صَرَفْنَآ إِلَيْكَ نَفَراً مِّنَ الْجِنِّ يَسْتَمِعُونَ الْقُرْءَانَ

یغْفِرْ‌ لَكُم مِّن ذُنُوبِكُمْ (will forgive your sins for you,) The word 'min' used in the text gives the sense of 'some'. If it is taken in this sense here, it would mean that 'some sins' will be forgiven by embracing Islam. It will indicate that only sins relating to the rights of Allah would be forgiven but not the rights of people. But some exegetes have taken 'min' in this verse as an extra word that has no additional meaning in Arabic idioms. Given this interpretation, no explanation is required.