If you have downloaded and filled the form then you just need to make this changes and print, if you have done this online you need to fill it again and print .
You have to make sure the signature date is not 90 days old when they receive the application again.
If not an issue, just add that on the current form they sent back.
Thank you for the replies . I called cic they told me to fill out a new form with new presence calculator because i only have 7 days left . So i filled the new form with updated dates just to be on safe side .