There are two ways of displaying the number of weeks in Flo: Current and Completed. For example, if you’ve set Current, and Flo shows week 40, it means that 39 weeks have passed and week 40 is in progress. If you choose Completed, Flo will show how many weeks have passed. Users from different countries have their own preferences for the way they count the weeks.
When you activate Pregnancy mode in Flo, Current week is shown by default. However, you can change it in Settings (in the circle) > Displaying of weeks > Choose Completed.