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- "By lines" prorated percentage adjustments are split so evaluated against the invoice sub-total and the resulting amount is distributed among the lines. So 10% is split across N invoiceLines such that each gets (1010% * invoice.subTotal)/N)%
- "By amount" prorated percentage adjustments aren't split but rather each invoiceLine gets an adjustment of that percentage... (e.g. if the invoice adjustment is 10%, each invoiceLine gets an adjustment of 10%.)
- "By quantity" prorated percentage adjustments doesn't make sense and the UI should prevent the user from using that combination. We will also need to validate this on the backend and return an error response in the case where someone makes a call directly to the API with the combo.
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