The manager of this staff can approve or disapprove his/her submitted leave applications. If "Leave form approval required" option in system settings is set, then only approved leave applications will be counted into total leave taken summary.
If you are an administrator user, you can enter edit mode of this report by clicking on "Edit Mode" to modify submitted items. Only leave type and reason fields are changeable. If leave start date or end date has to be changed, then you need to delete the old leave form and add a new one to replace it.