Row Source Operation VS Execution Plan

I traced one concurrent program that was showing FTS for a table although columns in WHERE clause were already indexed.

In the trace I found a strange thing


Rows     Row Source Operation
-------  ---------------------------------------------------
      0  TABLE ACCESS FULL RA_CUSTOMER_TRX_LINES_ALL (cr=0 pr=0 pw=0 time=0 us cost=76815 size=30 card=2)


Rows     Execution Plan
-------  ---------------------------------------------------
      0  SELECT STATEMENT   MODE: ALL_ROWS
      0   TABLE ACCESS   MODE: ANALYZED (BY INDEX ROWID) OF 'RA_CUSTOMER_TRX_LINES_ALL' (TABLE)
      0    INDEX   MODE: ANALYZED (RANGE SCAN) OF 'XXRA_CUST_TRX_LINES' (INDEX)

Query:

SELECT
RCTLA.QUANTITY_ORDERED - NVL(RCTLA.QUANTITY_INVOICED,0)   
FROM
APPS.RA_CUSTOMER_TRX_LINES_ALL RCTLA