Underneath the record button is the PLAY button on the screen. This should allow you to preview the content from the card on the aircraft.
The remote, aircraft, and device should be powered up when viewing the clips.
If you'd like to save a clip to your device, there is a download icon that will transfer the content from the card on the aircraft to your device.
I don't have a Galaxy tab a8 but the procedure should be the same. ?