This page explains how Sean Koster (USATT# 212045)'s rating went from 1604 to 1587 at the US Open held on 17 Dec 2017 - 22 Dec 2017. The links below take you to pages that describe various aspects of the rating processor.

The rating processor goes through 4 passes in order. The links take you to pages that provide detailed explanations of the calculations during each of the 4 passes.