But, and it's a BIG BUT,,,,,
If you've been out for only 1 hour, you can divide that 1000 kCals by eight to arrive at a sensible nutritional reward value.
So it's 125 kCals for the first hour. Or two fingers of KitKat....
As the rides lengthen, it's a 'sliding scaler' until the Garmin figure can be eaten in its entirity. For me, this is at 220 km ( a reasonable Brevet 200 ) and the Garmin figure is 4500 kCals.