Your DataCamp streak and XP on mobile reflects your account on the web version, however your course progress does not represent work done outside of the app.
If you completed a course via the mobile app, you'll notice a mobile indicator in the top right corner when you go to the desktop view, indicating that you finished the mobile version of the course. You'll also see a progress indicator for your desktop.
Note: Both mobile and desktop content contribute to your total XP; for example, if you complete the first chapter of a course on a desktop and subsequently complete the corresponding chapter on a mobile device, you will get XP for both.