To fill time while updating task progress:

Go to your Project.
Click Tasks from the list of project specific reports view.
Point at a task and click the action drop-down
Click on Add Update.
In the %* box, type the % Complete.

If the % Complete box is grayed out, it means that the task progress can only be updated via the time-entries.
In the Hours box, enter the hours as HH:MM. You can pick appropriate timecode from here.
Selecting/De-selecting the Send for Approval will Send or Save the time-entry accordingly.
Enter update comments in the text area provided.
Click on Submit.

The details of all the updates can be seen in a Task Update report. You can see updates for a particular date/date range by adding the Date filter.

The comments entered when entering a progress update can be edited from the Task Update Report.

To edit the task update comments:

Create a Task Update report.
Add filters like 'Date', 'Update By' to see the update you want to edit.
Under the Comments column, click on the actions drop-down .
Click on Edit.
Remove/Edit the original comments to add new ones.
Click on Save. The new comments will be added to the update.

Only the user who has added the comment will be able to edit them. The PM or any other administrator user cannot perform this operation.
The PM/Approver will receive every time changes are made to the comments.
The comments added against a time-entry is not editable.
To delete the existing comments, edit and remove them. Save the changes.

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