This chart is situated in the Customer Overview, and it displays how many weeks before the show your clients are buying their tickets. The information in this graph will help you understand the best time for your marketing campaigns.
The example provided can be used to create a use case.
Based on your launch date and analysis of past purchase behaviour you should be able to figure out not just when to approach your potential buyers, but also to make sure you segment them into early buyers/impulse buyers and adapt your communication accordingly.
As we can see here, customers start buying tickets 20 weeks in advance, and the trend increases rapidly until the week before the event.
Based on this information, you can for example decide to send out one campaign 12 weeks before the event to early buyers and a second one the week before to promote the unsold seats to those who buy only a few days in advance.