According to the article, it took them a half hour to shut it down. That's more than a few seconds.
But as a torrent of faulty trades spewed Wednesday morning from a Knight Capital Group trading program, no one at the firm managed to stop it for more than a half-hour.
Technically, it can take seconds to lose that much.
What they did wrong is do all their trading with the same algorithm. Way to put all eggs in one basket.