This is a 90 min Postbox 'start anywhere' challenge. Score 20 points per checkpoint visited with a 10 point penalty per minute over the allowed time. The map has a start/finish marked as a triangle and double circle and is located at a postbox. The start point will not count towards your score. However, you can use any checkpoint as your start. If you do this, that point will then become your finish and it will not count towards your score. However, the marked start/finsh will then become a scoring checkpoint.
Further instructions here
On your app 'Select Event'