From the original post:

Rachel does not envy Irene her choice at all. What she wishes is to have the one-boxer's dispositions, so that the predictor puts a million in the first box, and then to confound all expectations by unpredictably choosing both boxes and reaping the most riches possible.

Richard is probably using disposition in a different sense (possibly the model someone has of someones disposition in my sense) but I believe Eliezer's usage was closer to mine, and either way disposition in my sense is what she would need to actually get the million dollars.