Similar to the views calculation the completion rate is based on the unique users per session that have completed the guides. We define the guide as completed when the user sees the last step of your guide.
Note: The user doesn't have to leave feedback for the guide to be counted as completed.
The formula for the completion rate is:
Unique completion events / Unique views
If someone goes through the guide multiple times and completes the guide this will not be counted multiple times.