'Fine-tune' allows you to adjust staff or resource hours on select dates. For example, if a staff member generally works Monday to Wednesday but they are required to work on a Friday, you can fine-tune their working hours.
Go to the Calendar, select the relevant staff or resource that you want to change. Click on the ‘clock icon’ (as shown in the circle below) and select your desired hours. If you want to apply those hours to additional dates select on ‘Apply these hours to other dates’.