Open Quantity Column in Marketing Document

Dear All

While going through the table structure of Marketing Document I found that there are two column - one is 'OpenQty' and another is 'OpenCreQty'. Both the columns kept the same values.

Will you please let me know the utility of keeping same value in two columns or what is the interpretation of 'OpenCreQty' column?

Thanks

Aloke Bandyopadhyay