20.28 实质性会议服务方面出现差异主要是环境政策委员会的会议造成的，原因是：(a) 决定将其 2018年年度会议日期改为 2019 年 1 月，并将其年度会议的会期缩短为最多六次为期半天的会议；(b) 多边环境协定缔约方会议周期。
20.28 The variance in substantive services for meetings is driven mainly by meetings of the Committee on Environmental Policy, owing to: (a) the decision to move the date of its 2018 annual session to January 2019 and to shorten the duration of its annual sessions to up to six half-day meetings; and (b) the cycles of conferences (meetings) of the parties to the multilateral environmental agreements.