When your watch is showing a six-digit code, this indicates that a nearby mobile device such as a smartphone, tablet, or iPad, is attempting to connect with the watch. This can occur in the following scenarios:

While completing the initial setup to pair your watch with a mobile device
If set up with a mobile device was started but wasn't completed
If the watch has been paired with more than one nearby mobile device

If a six-digit code continues to appear on your watch when you are not actively attempting to connect it with a mobile device, follow the steps in Removing and Adding a Fitness Device in the Garmin Connect App to completely unpair or remove the watch from all nearby mobile devices, then pair or reconnect the watch with the mobile device you plan to use with the watch moving forward.