There is an academic update time period sometime. This year (er last, I guess) it was November 17.
You submit your grades when you apply in May, then you can no longer change your grades until the academic update. You can then update your grades once (so if you update your summer grades on November 17, and your fall grades are not in yet, you will not be able to submit again).
You would be able to ENTER your summer grades in, and not click submit until you get your fall grades.
Hope that helps.
