This page explains how John Zydell (USATT# 24233)'s rating went from 1500 to 1480 at the Patuxent River League event from 27 May 2004. 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.