Invoice Amount Due

SOLVED

Hello Team,

Could you help me with the following question?

I created an Invoice.

On UI I see the following balances:
The Document Total is $2.55.
Amount Due is $2.51

But, when I receive this Invoice from post documents via API, Sage returns the Invoice Amount Due $2.55. And the Customer Balance is $2.55.

{
            "CustomerNumber""CUSTOMER1",
            "DocumentNumber""INVNUMBER1",
            "CheckReceiptNumber""",
            "OrderNumber""",
            "PONumber""INVNUMBER1",
            "DueDate""2021-09-29T00:00:00Z",
            "NationalAccountNumber""",
            "ShipToLocation""",
            "TransactionType""InvoiceItemEntered",
            "DocumentType""Invoice",
            "BatchDate""2021-08-30T00:00:00Z",
            "BatchNumber"173,
            "EntryNumber"1,
            "GroupCode""EMP",
            "DocumentDescription""1",
            "DocumentDate""2021-08-30T00:00:00Z",
            "AsofDate""2021-08-30T00:00:00Z",
            "Terms""P90",
            "DiscountDate""2021-09-09T00:00:00Z",
            "CurrencyCode""CAD",
            "RateType""SP",
            "RateOverridden""No",
            "ExchangeRate"1,
            "FunctionalCurrencyInvoiceAmount"2.55,
            "FunctionalCurrencyAmountDue"2.55,
            "FunctionalCurrencyTaxableAmount"2.25,
            "FunctionalCurrencyNonTaxableAmount"0.000,
            "FunctionalCurrencyTaxAmount"0.3,
            "FunctionalCurrencyDiscountAmount"0.04,
            "CustomerCurrencyInvoiceAmount"2.55,
            "CustomerCurrencyAmountDue"2.55,


Why on UI do I see Amount Due is $2.51? And why amounts don't coincide?