I got this from the Equity website. Hope this helps.
"Referenced to the Off-Broadway Agreement and limited to theatres of not more than 199 seats, the New York City Letter of Agreement (LOA-NYC) is specifically designated for use by seasonal, non-profit theatre companies.
Although the terms and work rules of the LOA-NYC are established, the weekly minimum salaries are individually negotiated between Equity and the theatre companies. Approximately twenty New York City theatre companies use the LOA-NYC."