This page explains how Michael Guo (USATT# 221417)'s rating went from 2249 to 2219 at the 2021 HITTA Butterfly Halloween Open held on 29 Oct 2021 - 31 Oct 2021. 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.