How is initial claim for unemployment insurance a leading indicator, and average duration of unemployment a lagging indicator

Hi guys,
Title.
I don’t really get. So i understand that unemployment figures are not necessarly giving any predictive information in the sense that employers wait for economic downturns to be confirmed to start laying off people, and economic upturns to be confirmed to start recruiting.
But why would initial claim for unemployment insurance would be a leading indicator (source everywhere and CFA book), to me the same rationale should apply to it, if there are too many unemployment insurance claims, it means employers laid off a lot of people because everyone already knows there is an economic downturn.