Please be reminded that once you have approved the Leave Application of your staff you cannot cancel it. The person who applied for leave has to apply for cancellation. Once he or she has submitted the cancellation request, then you will be able to approve it. You will receive notification emails about the cancellation request.
If you are not sure about the Leave Application of your staff and you need more time to think about it, you may select Tentative. But make sure you come back to it and do the necessary approval or unapproval.
Now the status of the leave application entry in the table will becomes 'Approved' and will have a green background.
See images below for sample illustration