I have a full screen image gallery that is opened via js when a user interacts with an image on the page. When this occurs, we fire a GA Virtual Page view, which we can view in analytics.
I can see the impressions for this fine in GA but I also see an Average Page Load(secs). How is this calculated? I would assume on a standard page view that this is the time until the window.onload event fires, but I'm not sure what this time is measuring when a virtual page view is fired later.