Scheduled Tasks vs Log File

[Jerry]

Scheduled Tasks –

I schedule a number of tasks such as Defrag, Scan Disk, Virus Check, Disk
Cleanup, etc.

When I view the Scheduled Tasks menu that lists all of my scheduled tasks
and their run times, it will indicate in one column the last time it was run
and in another column the time for the next run time. So, from that listing,
I assume if I see an entry in both time columns, the task was completed.

Now, when I select the Scheduled Log file for scheduled tasks to check on
this, I do not see listed all of my scheduled tasks. For example, my Log
file did not list Defrag, Disk Cleanup and Scan Disk in the Log file.

So, my question is why does my Scheduled Task menu indicate all tasks have
run as scheduled, but the Scheduled Log file does not list them all?

Thanks,
Jerry Reeder