Dear All,
Got the error myself
Highlighted part in following screen shot (of respective form) was not created by me.
So the system was giving all the documents for the particular customer, when I clicked on goto line items in the report created (based on the form)
In another way it means that we need to specify "number of days" for line items which are not due
as well.
Br,
Sapan
PS:Not sure, if it is ethical to mark own answer as correct as per the SCN guidelines, therefore will try to mark it as assumed answered