It's always a good idea to uninstall the debug version of the game from the device and install the production version. We should never publish the APK without checking it first even if the changes made were simple, because the export process, in rare cases, introduces errors to the APK.
To install the APK, the adb command-line tool is used. The Unknown sources option must be enabled in the security settings of the device. The APK can be installed using the following command:
adb install LearningAndEngine.apk
You can also send the APK to yourself via e-mail. Opening the attachment in a Gmail app will let you install the APK.