Thanks, I see
Excuse me for the confusion.
Originally the idle time was not included in the report in old versions, but some users asked to include the idle time, which measured since the last user input. This should reflect how long the system is inactive (not performing user actions), not used. This may be used to determine if the systems are still running - but inactive and admins can enable different power management settings (to enter standby after long time of inactivity) where appropriate.
I did not know the other tool shows cumulative idle time. Personally I do not really feel it is useful (know no real uses), especially that the total system uptime is also displayed in the report. So that may show how long the CPU is really idle - which may be interesting, but yes, this is different from the "idle time since last user input" which is included in Hard Disk Sentinel report.
Thanks for your attention anyway and excuse me for the possible confusion