How to adjust the total amount in purchase bill or purchase order

How to adjust the total amount in purchase bill or purchase order

Hi..
i am new to zoho books and want to know,
1) How to adjust the total amount in purchase bill or purchase order.
It only can be adjusted in Invoice but not in purchase bill or purchase order.
2) How to show Final amount in words on invoice.

screenshots are attached here with....

plz reply soon.