A Breakdown Of The New Cumulative Layout Shifthttps://blog.webpagetest.org
We saw that the CLS metric in CVW was recently modified.
This posts break it down and gives you more info on how it works.
Up to this point, CLS has been the sum of all individual layout shifts (that weren’t preceded by user interaction) during the time the metric was being recorded (page load, entire page session, etc). Going forward, however, they will instead break that session up into “windows” of shifts and then report the maximum score of each of those windows as the CLS score.