All the issuance related operations ( Create, Reset, Reissue, Fetch) are tracked through the ARWFISSUANCEAUDITLOG table and Actual credentials are stored in ARWFARCOTID table.
You can run a report "Credential Management Report" which will show if users are changing their PIN or creating.
If you reset the PIN a new ArcotID is created as with the PIN the ArcotID keys are camouflaged so a PIN change will indicate a new ID for the same user.
In ARWFISSUANCEAUDITLOG table CredID will contain the existing credid and NewCredID field will have the credid which is changed and became new.