Well, as TonyArra says, these machines always overstimate the amount of calories burnt.
Also, you have to take in account that if you start your workout with the elliptical, this is, you don't do muscle workout first, you won't start burning fat until the first 30 min. So if you workout for 60min, you will burn fat for 30min.
So you will be really burning around 200 calories from fat.
Edit - Calories meassurement
First you should calculate your basal metabolic rate (BMR). This tells you how much calories do you burn just doing normal life (these values are just an aproximation). But this is a dificult value to meassure, as you need to be in a dark room, after sleeping for 8 hours, etc... So you can measure your resting metabolic rate (RMR) which will tell you almost the same and it's easier to meassure. You can use one of these 2 equations for male:
After this, you should apply the activity factor, which indicates your daiary activity value (not exercise):
- 1.2-1.3 for very light (bed rest)
- 1.5-1.6 for light (office work/watch tv)
- 1.6-1.7 for moderate (some activity during day)
- 1.9-2.1 for heavy (labor type work)
Then do: Diary activity cost = RMR * Activity factor
And finally we apply the phisical activity factor in Mets:
- high impact aerobics: 7
- low impact aerobics: 5
- high intensity cycling: 12
- low intensity cycling: 3
- high intensity walking: 6.5
- low intensity walking: 2.5
- high intensity running: 18
- low intensity running: 7
- circuit-type training: 8
- intense free weight lifting: 6
- moderate machine training: 3
Then do: Diary exercise cost = Weight(kg)*duration of exercise(hours)*Mets
Finally: Total exercise cost = Diary activity cost*Diary exercise cost
This will give you an aproximation of the amount of calories that you burn in a day.