Amount  

This is an optional field. It defaults to Quantity * Rate rounded to the precision of the system currency. You can directly enter/override the amount. If you override the calculated value, the system will not recalculate the rate. The Document Totals section at the top of the page will get updated with this amount. The amount can be positive, negative,  or zero.

Changes to quantity or rate should trigger recalculation of amount value if both quantity and rate are specified. However, changes in amount value do not trigger any other changes.

If the PO is associated with a PR,  and Control Purchase Order Amount (in the related PR summary) is set to "Detail Lines", then the sum of line Amounts for a PO line must equal the sum of line Amounts on the PR lines. If Control Purchase Order Amount  is set to "Summary", then the sum of line Amounts for a PO line can be less than the Request Amount from the PR, but cannot exceed it.