The phone’s camera roll shows there are 1000 photos in it, but only 500 photos are shown after imported to iData. The reason for this is that those 1000 photos shown in the camera
roll include Photo Stream photos, which are temporary files being pushed from iCloud drive instead of source files. So they cannot be exported directly to iData. Prior to exporting Photo
Stream photos to iData, please make sure to download/save the Photo Stream photos to the phone’s camera roll.