About Sen. Johnson's town hall 600,000 participation claim

I noticed this Ron Johnson Tweet last week which was republished around the state.

@SenRonJohnson  Feb 24More 600k Wisconsinites have particiapted in @SenRonJohnson telephone town halls. Here's audio from the last one:

Johnson credited some "amazing technology," though he also noted how few questions were actually posed: 

Friday Sen. Johnson tweeted out that 600,000 Wisconsinites have participated in his telephone town halls. And he posted a recording from the latest one, held on February 16, where he took questions, including several about the affordable care act.

“To date, by the way this is just amazing technology, we’ve dialed up to more than 3 million people doing these telephone town halls, more than 600,000 people have participated in the town halls,” Sen. Johnson said during the telephone town hall. “I’ve answered so far 821 questions. “

So I asked Johnson's media person Ben Voelkel this question by email this week: 

Media last week reported that Senator Johnson had said on Twitter that 600,000 Wisconsinites had participated in telephone town halls. Can you explain how that figure was ascertained and provide any documentation or descriptions of methodology used to support the figure? 

Voelkel responded this morning:

The conference call service sends a tally of how many people participated in the each call and then we keep a running total. 

I still couldn't figure out what "participated" meant. I should have asked a better question.

For example, if a person's number was called, but not answered, or did not produce a call-in were they still in the participation tally?

So I wrote back to him a few minutes later this morning:

Thank you. And not to split hairs, but does "people participated" mean people who called in, listened and perhaps also asked a question, or does it also include people who were contacted but did not actually call in or ask a question?

Also - - do you have the number of these sessions over the years?

Thank you, again.

No response yet.

If I get any more information, I'll post it.