There are two ways to mark a customer as having walked out prior to service.
Find the customer you wish to mark as having walked out, and swipe the customer card to the left. This will expose additional features, one of which is marking a customer as having walked out. Simply click on the walkout button.
Click on the customer card that is currently in the Queue.
Upon selecting the customer the customer details page will now appear.
Press 'Walkout' located in the bottom right of the device. By pressing this the customer will be removed from the queue.