How are you calculating the 'average daily velocity' here?

[Claire Hannon]

This question is in reference to Atlassian Documentation: Viewing the Version Report

Our version reports are always more pessimistic than I believe they should be. How do you actually calculate the 'average daily velocity' mentioned here? I would like it to be a 3 sprint rolling average, but I think it might take all the previous sprints. Where the team spikes at the beginning of a project or changes size this is not appropriate, but more worrying is that it is unclear. What measure is actually being used? 

[Charles Bradley]

This blog post has a theory about how it is being calculated, and why the prediction line will sometimes "bend":  https://www.alfresco.com/blogs/developer/2015/07/29/inside-the-jira-version-report/