I think the "verification data" is a string of characters that the voter can read off the ballot and either commit to memory or note down on a piece of paper th

I think the "verification data" is a string of characters that the voter can read off the ballot and either commit to memory or note down on a piece of paper they bring with them. Importantly, though, there are as many strings printed on the ballot as there are candidates, so there is nothing stopping the coercee from noting down the string that corresponds to the vote they were told to cast, without actually casting it that way. I'm not sure how this still gives rise to the claimed properties of the system, but the inventors did at least take the coercion problem seriously, from what I remember.