It is fine - do not worry about it.
things happen and sometimes you may need to reschedule. It is actually not bad either way (canceled or low score), which if an admissions committee has a brain, they will equate but will figure something unusual took place, so nothing to get hung up on. However, as I said - do not worry about it at all.
The adcom will ask for the score
You will put the highest score into your application.
They will verify that you indeed have that score (one of their student workers most likely)
That's it. Only if you are very similar to a large pool of applicants will they dig into your score reports and look at it, which again, don't think is an issue at all.
So, get some sleep - feel better and good luck next month!
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