On Top40Weekly.com, for the chart “US Top 40 Singles Week Ending 12th December, 1970”, the number of weeks on the chart for the No. 1 single that week (i.e. “The Tears of a Clown” by Smokey Robinson and the Miracles) shows 8 weeks. But if you check the Top 40 Singles chart for the previous week (“US Top 40 Singles Week Ending 5th December, 1970”), this same single also shows 8 weeks on the chart. This is obviously an error, and it means that every “weeks on chart” value for this single is off by one for the remainder of its chart life through early 1971 (starting with the 12th December, 1970 chart).