Хелп хотя бы иногда надо читать.
You can append and delete records while table buffering is enabled: appended records are added to the end of the buffer. To access all records in the buffer, including appended records, use the RECNO( ) Function. The RECNO( ) function returns sequential negative numbers on records you append to a table buffer. For instance, if you initiate table buffering, edit records 7, 8, and 9, and then append three records, the buffer will contain RECNO( ) values of 7, 8, 9, – 1, – 2, and – 3.
То есть -1 и есть номер новой строки.