Would the OP or someone else familiar with the site be able to provide more insight on the data? The site also allows users to submit layoffs so the data is crowdsourced too:
Worker Adjustment and Retraining Notification (WARN) Act says layoffs of >100 FTE within a 30 day window have to be reported 60 days in advance. California state law is even stricter at >50 FTE.
Would the OP or someone else familiar with the site be able to provide more insight on the data? The site also allows users to submit layoffs so the data is crowdsourced too:
https://layoffs.fyi/share-layoff-intel/