Why so many different file sizes for DJI GO APK 2.8.3?

[Clemens]

Hello, I was having heavy trouble with the latest updates and wanted to go back to
DJI GO APK 2.8.3. There are plenty of apk mirrors, but all having different file sizes. Any ideas why? Am I doing something stupid here, like getting me a tampered apk?

Thanks for any suggestions!