Err... the operative phrase is "before the EC-Council security team was able to respond to the breach". They might have spotted the breach while it was on-going and moved fast enough to block things before all accounts could be ransacked. Remember, it takes time to download stuff. Depending on how much data was in each account, and how fast the upload speed on the site was/how fast the download speed on the hacker's side was, the hackers may have been interrupted before getting it all.
Now, exactly how big 'a small number" is, well, that's open to question. Ten? A hundred? A thousand? A 100,000? If you use Obi-wan Kenobi's point of view, a small number could be just about any number you like. Personally, if I had my data on that site (and I don't) I'd want some actual hard numbers on this. But that's me.