Overall progress is shown on an individual user's Report Card as a percentage. It represents the percentage of completed courses out of the total courses the user is currently enrolled on.
It's calculated using a user's total current enrolled courses, so it doesn't include historic courses.
If an enrolled course has a training interval and the user's training has expired, it's marked as not completed and included in the calculation.
How to find overall progress
Go to Reports.
Find the user and click on their email to open their User's profile.
The REPORT CARD is at the top of the page.