I'm trying to work out the right rotation for a lvl 50 BLM, and I'm encountering a small problem I don't understand. When I try to add thunder I to my hotbar, the game automatically converts it to thunder III. Am I not supposed to be using TI at this point? I thought it was still a useful filler at times.

I'm not level shifted down or up, just at level 50 in Ul'Dah. I tried to look this up, but apparently my misunderstanding is so basic, I'm the only one who doesn't get it...