Hi,
Basically this is a similar issue to the one I had a while back, only now with the outdoor cycling program. The watch will duplicate calories by uploading not only the activity calories but also some other mysterious active calories even when it's not being worn, but is being used as a bike head unit. A 400 calorie bike activity will show about 800 active calories making calorie tracking for food intake vastly inflated.
A corresponding indoor ride will however register the correct 400 or so active calories on an otherwise sedentary day. Calorie syncing is once again broken in Garmin Connect and such a core functionality being useless does not paint their QC in a favourable light.