co-chair a session in a conference-- does it help for EB1-A

[theyesterday]

I recently attended a conference (100-200 people). They asked a senior person as a chair and a junior person as co-chair. I was one of those juniors to serve as co-chair in one small session. Should I include this in my package? And how should I justify?

Another question: are conference posters counted as publication/contribution?

Thanks a lot for any inputs!!