Quantity Discount

Dear Experts
We purchase Raw Material in bulk quantity from a supplier. After 5-6 purchases, The Supplier gives us Discount based on quantity in a month and issues a credit note but without levying any gst on it. How should we treat it as we claim all itc when we purchase goods from him and same gst amount also get reflected in ours Gstr-2A but credit notes are not reflected there.
Whether we should reverse the ITC or do any other treatment of it.