I've used Garmins and similar and myfitnesspal to lose and now maintain weight. Yes, its not perfect and not a 'lab accurate' guage, and yes, calories are a very imperfect measure of nutrition but all that being said... The things that I have noticed:
Having a cycling activity with HR run whilst I'm not cycling generates a higher number of calories than my basal metabolic rate suggests it should; so I do try and avoid long periods of not cycling when recording.
Different devices (even from the same manufacturer) can have very different algorithms.
Changing age / height / weight / activity class on the device can radically change the results.
However, assuming both rides either side of your highlighted ride were on the same device and you didn't change the config of your device then it does look very wrong - the time, avg HR and distance all suggest they should be within a few calories... Personally I'd ignore it unless it starts happening more often and if it does try Garmin support (who will tell you to go away and reset the device before even reading your email

)