I was told once that if you have a few different things to dispute on the same account that you can dispute all of them at once, but that it's best to dispute on thing at a time. That way if for whatever reason the OC verifies the first one, then you dispute the next one, and so. If you dispute all of them at once, then you have nothing to dispute later if the OC verifies them. Supposedly the chance of getting it deleted is better if you dispute one at a time.