To see a conflict resolver screen, the following steps need to have happened:  

  1. Created a save slot on your first device  
  2. Continued playing the same save slot from your second device
  3. Returned to your first device to continue playing

This screen simply means that the local save on your original device does not match the most recent data uploaded to the cloud from your second device. Here you have the option to keep the old data or your new data.