Correction to my earlier post. After reading other posters, I watched the video again, and my fellow FReepers were right about the machines being able to read 3000 ballots per hour. Based on that, each suitcase probably contained about 6000 ballots, and there were 24,000 ballots in all.
Somebody said after watching carefully that some stacks of ballots were run more than one time. Doesn;t change your total, but could change the number of ballots needed to keep the machines busy.