You shouldn't use a device as an end all for calorie tracking. That will end in failure. Use the scientific formulas
The "scientific" formulas are inaccurate too, unless you only eat industrial and over-processed food since it tends to be very normalized.
For instance, you can have very different wines that are only a few kilometers apart. One of the reason is exposure to sun or to rain. Because more sun means a different grape - more sugar for instance (and so more calories).
Likewise, if you eat meat, you know that chicken or cow have a different tastes (mostly due to the quality of the fat and muscle), depending on whether they were in freedom or in battery. Likewise, race or feeding also has an impact on fat content and fat quality.
It's very easy to give the caloric content of Nutella down to the single digit, but it's very difficult with natural products...
When you look at a calorie table, all the grapes in the world have the same sugar content and calories... All the same cut of cows in the world have the same fat content.
And on the other end, depending on intestinal flora, not everyone digest exactly the same way. And depending on training, you don't spend energy the same way.
Calorie table and calorie expenditure table only show an average - individuals and foods can vary a lot from that average. Averages should be used to assess averages, not to determine individual actions.
The only scientific method of calculating calories is to use a calorimeter and it's expensive and impractical. The only precise method is our brain which has a lot of redundant inputs to assess energy homeostasis.
That's why the calorie reading on exercising devices is the most meaningless. There is no way it can be precise or even useful. There are much more useful readings, such as your heart rate compared to your energy output or how fast your heart rate decreases when you stop, because both are good indicators of progress and cardiovascular health.