The availability of an employee is calculated on the basis of 3 aspects with following priority:
Availability as filled in by the employee himself (in the menu under My schedule - Availability).
The approved leave of the employee. This leave can be requested by the employee himself or filled in by the chief.
The standard working hours of the employee (in the menu under Management - Users).
An overview of 1) the filled in availability and 2) the leave is available in the menu under Schedule - Absence & Availability. But first you need to check 'Show extra availability'.
When planning, availability will be shown in the lists Available and Unavailable in the dayview.