I still don't know where you get the six endings...
BAD ENDING
(SPOILER)Shuyin kicks everybody's butt and Spira eats it.
SAD ENDING
(SPOILER) Yuna says bye to Tidus
NORMAL ENDING
(SPOILER)Yuna sitting on the ship after it takes off from Lucca
GOOD ENDING
(SPOILER)Yuna finds Tidus, they run, they hug, the love I cry.
PERFECT ENDING
(SPOILER)Yuna and Tidus in Zanarkand ruins.

Unless you're counting the Shuyin and Lenne thing, thats just part of the game, not an ending. I still count 5.

You automatically get the normal ending before you see any of the good/perfect endings. The perfect end you see Normal, Good and Perfect in that order. There are still only 5, set up in three combos.