If you have been requested to complete an additional payment for whatever reason, here is how you do it.
The number of units refers to the number of $1 units in the custom payment, not the number of items you will receive. E.g. if you need to pay another $16 USD, then you need to change the number of units to 16 (16 x $1 = $16). The number of items you ordered will not change.
If you have been requested to provide a payment number, this is the order number you need to give us:

Date Modified 2020/12/06