Roughly zero, if the scale as a layoff would be sub-WARN Act level, because it is unlikely that the impacted employees had any contractual severance guarantee or any legal entitlement to any notice of termination of employment or pay in lieu (they might be less than the firm’s historical practice for similar roles, and having an excuse to characterize it as voluntary provides a bit of PR cover for that, but that's not a legal or contractual guarantee.) At-will employment is the rule, rather than the exception, for private, non-uniom employment in the US.