A background task runs every hour to verify the calculated final grade (CFG) for each course where grade items have recently changed and the CFG is set to be kept up to date. The audit log lists any CFG that was incorrectly calculated (Previous CFG), and the change that has been made to correct it (Corrected CFG).
Viewing the log requires the See the Final Grade Audit Log permission, which is off by default for all roles. The log data contains username values. If your organization does not allow administrators to view usernames due to user information privacy, it is recommended that you do not grant this permission.
Once you have this permission, you can access the Final Grade Audit Log from the Admin Tools menu.