The event runs from Thursday June 19th until Friday June 27th. While that may seem long, in reality most attendees focus on the 4 days between June 22nd and June 26th.
On a call with community leaders last week ICANN’s CEO Fadi Chehadé said that this meeting was probably going to be the biggest in the organisation’s history. As a general rule meetings held in Europe are big in terms of number of attendees. Don’t forget, the meeting itself is free to attend.