This might be old entries which was not cleared properly in SEPM database. Try to check the Logs on SEPM for these computers having false data in reports or not.
If Logs too showing the same data then check the agentinfo folder.
Location: C:\Program Files\Symantec\Symantec Endpoint Protection Manager\data\inbox\agentinfo
Clients will send the dat files to the SEPM, Those DAT files will have the client information which should be processed by SEPM and purged within a minute.
If you see .err & .tmp files. It indicates SEPM is not processing the client DAT files.
Then you need to
- Stop the SEPM services
- Delete those .err & .tmp files manually
- Start the SEPM services.
Delete the client entry from SEPM so it will connect and register again.
Now Pull the report and check with the information......................