Technical Tip: The 'sn' field does not appear correctly in admin login/logout log

This article describes that in the FortiOS Log Message Reference 6.4.9 or 6.2.x, the 'sn' is 'Serial Number':

https://docs.fortinet.com/document/fortigate/6.4.9/fortios-log-message-reference/32001/32001-log-id-admin-login-succ
https://docs.fortinet.com/document/fortigate/6.2.10/fortios-log-message-reference/32001/32001-log-id-admin-login-succ

But the actual log shows 'sn' field does not display the 'Serial Number'.

Admin login successful log:

date=2022-05-11 time=17:24:28 eventtime=1652261068911558863 tz="+0800" logid="0100032001" type="event" subtype="system" level="information" vd="root" logdesc="Admin login successful" sn="1652261068" user="admin" ui="https(10.176.2.173)" method="https" srcip=10.176.2.173 dstip=10.176.2.171 action="login" status="success" reason="none" profile="super_admin" msg="Administrator admin logged in successfully from https(10.176.2.173)"

The 'sn' in login/logout log means that the login/logout event serial number in Admin login/logout log, is not the actual serial number. 

It is confirmed that there is no serial number in login/logout log.

The 'sn' field for login/out event it is used to correlate login/logout events.