This page explains how Mark Johnson (USATT# 26863)'s rating went from 1853 to 1851 at the ICC Juniors and Adults League event from 15 Sep 2008. 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.