Why do the file sizes of photos and videos in MB uploaded to the Koofr mobile app for iOS seem smaller than those on my device?

Apple converts bytes to kilobytes by dividing with 1000 and Koofr does it correctly with 1024. Because of this, size in MB on Koofr may seem smaller than on iOS, but it is actually same in bytes. Try downloading the picture or video back to your iPhone and check its size - it will be the same as before upload.