If a user enters my site from a referring site (siteA.com) then within 30 mins is referred from another website (siteB.com) is this counted as 1 session or 2. For instance would the session be broken if the user was handed off to a 3rd party payment service and then referred back to the site?
In this scenario Google Analytics Universal Analytics will interpret this as 2 sessions, while Google Analytics classic will report 1 session.