Garmin Connect showing negative active calories after importing Fitbit data

Hi all,

Brand new Garmin user here :) Just switched to a Garmin watch this week after using Fitbit for 6 years straight.

I'm trying to import my Fitbit data (which turned out to be quite a challenge...). I finally managed to import some data, but I just noticed something weird happening to the calorie count.

I have the actual import CSV-files, so I can see the exact amount of calories on any given day, but these don't match what Garmin Connect is showing after import.

For example: 

On 15 september, the imported CSV file shows:

Date Calories Burned Steps Distance Floors Minutes Sedentary Minutes Lightly Active Minutes Fairly Active Minutes Very Active Activity Calories
15-9-2024 2,015 8,064 0 0 506 344 0 0 975

while Garmin Connect shows:

(My language is set to Dutch, but I'm guessing you get the gist ;) )

The 1,040 "calories in rest" actually make sense, that's total calories minus activity calories (2,015 - 975 = 1,040)

But I don't have a clue how I would have burned -6,828 active calories...?

Any ideas?