This page explains how Will Foster (USATT# 214897)'s rating went from 1581 to 1559 at the 2021 HITTA Butterfly Fall Open held on 14 Aug 2021 - 15 Aug 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.