When we look at BQ Visualiser and look at a stage, we see that there is a property called "duration" ... see screen shot:

This confused me ... I wondered "a percentage of what?" ... at first I thought maybe of total time ... but as I clicked around, I found that many of my stages showed 80%+ and they can't all sum to be > 100%.

I then got to thinking that maybe this was a coding error and the property should simply be the end time - start time for the stage and that something is coded incorrectly. This issue asks for an examination of the story and either change the code or add documentation on the meaning of the duration.