Hi @Green Arrow
About audit log trimming, the default setting for retaining audit log data is zero days, that means if you don't specify a different retention period, all audit log entries are deleted at the end of the month (in the content databases in SQL). In addtion, we can also specify the document library to save audit log reports to before the audit log data is trimmed. Set this option if you need access to audit log data, using audit log reports, after the audit log has been trimmed:
For better understanding, you could refer to these two simialr case:
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