0FI_AP_4 Enhancement Logic

One of the documents 0FI_AP_4 extract is KD (Discount) documents,Which will be either Overider discount or settlement discount.

The standard extractor gets the document and Type,But won't idenfity wether the discount is of Overider or settlement.

In which table this information is stored and how can i enhance 0FI_AP_4 to include this information.

Thanks