Data API returns number using system's decimal separator, but in many countries, systems uses comma as the decimal separator.
Json specs specify that decimal separator must be a point
Regarding all systems that may consume json data this is a real problem for at least half of the world according to this article Decimal mark - Wikipedia .
Data API should never return numbers using anything else that point separator as it is a JSON Standard.
Found this issue when trying to use Data API with Tableau. I had huge differences between my database and Tableau's report.
After a while, I figured out that all floating numbers where imported as 0 value by tableau because of that decimal separator (all int values where imported correctly)