A walkout is a customer who has been identified as having left the queue BEFORE being called forward for service. You will need to mark these customers as walkouts in order to remove them from the queue.
In the queue, find the customer you wish to mark as a walkout and click on the customer card..
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.