For ITMS 8.1, the version of Software Update Plug-in Windows was showing the expected version as 8.1.6208 instead of 8.1.5620 for example on the SMP Console.
1) Use the following query to find the plugin GUID of the affected plugin/plugins
select distinct vi.name, svs.pluginguid, svs.version,svs.build from smpversions svs join vitem vi on vi.guid = svs.pluginguid
Note: '37D25576-7845-42A5-991C-D08D55D44414' is the usual GUID for Software Update Plug-in
2) Execute the below query to update the correct version as mentioned in article https://support.symantec.com/us/en/article.info4970.html
[Version] = '8.1.5620',
[Major] = 8,
[Minor] = 1,
[Build] = 5620
Where [PluginGuid] = '37D25576-7845-42A5-991C-D08D55D44414'