After entering your time tracking details:
You can save your record by clicking the green "Save" toolbar button. After clicking that button, a pop-up message will appear once your record has been saved:
This indicates that your timesheet save process has been completed, with your entered information now recorded on your server.
If you would like to change your recorded time and comments, just re-enter your timesheet screen and adjust your hours as you would like. After clicking the Save toolbar button again, your changes will be saved on your server.
Your timesheet can be updated and re-saved as many times as you would like until your record has been approved (and locked) by your manager.