In the EQ, it “snapshots” your prestige once you enter the quest for the first time. You probably increased your prestige since then, thus the discrepancy. Your profile prestige is the one that is “up to date”.
Personal example from my account:
EQ shows my Mr. Negative with 30870 PI, because that’s what it was when I first entered the quest. In my account, if I sort by prestige, my Negative has 31490 PI because I had dumped some sig stones into him later on.