the almost_picking status is one of the delivery status that Stuart is sending you in the delivery updated webhooks event as soon as the courier enter the pickup zone. This pickup zone is centered on the pickup location and has a customisable radius (from 25 to 3000 meters) per Stuart account.
To modify this almost_picking radius value just email your account manager with the desired value. They will also be able to advice you about the best value based on your needs and our experience.
Notice that this status is not mandatory during the delivery lifecycle.