Ledger Account No. 21001000 represent Accounts Payable and its balance = $ 1,000 which is a result of 2 invoices, one for Ven001 = $300 and the other for Ven002 = $700.
In the Journal that contains the Trial Balance that you are preparing for the uploading, you will remove the Ledger Account 21001000 line, and replace it with the two lines of type Vendor for both the Vendors Ven001 & Ven002, you could also specify the document date (to maintain the ageing information) and the Invoice# .
Other benefits you could gain from this method by specifing the actual currency of the Invoice and its exchange rate (Note: Invoice Amount in other that company primary currency must be equal to the AmountMST, and this is achieved by the proper exchange rate).
By this way you won’t need the 999 Ledger Account (You will use “999” account only in the uploading of Inventory opening Balance).