Because NetSuite allows for the Amount field on transactions to be overridden, care must be taken to maintain integrity using one of the two options below.
First Option: If you do not need to see the Amount field exclude it from your template.
Second Option: If you do need to see the Amount field know that if you change quantity or price you must also change the Amount value. This can be done with a formula (Quantity * Price) or manually.
If you do not follow one of the above options you will be able to successfully update the record but the Amount field may be inaccurate. You will, however, get a yellow notification in the (Reserved) column on the CloudExtend template returning the warning value from NetSuite which is typical The line total amount is not equal to the item price times the quantity. Is this correct?.