Just clarified this in the README:

* Input value ranges are as follows:

- Station name: non null UTF-8 string of min length 1 character and max length 100 characters

- Temperature value: non null double between -99.9 (inclusive) and 99.9 (inclusive), always with one fractional digit

* Implementations must not rely on specifics of a given data set, e.g. any valid station name as per the constraints above and any data distribution (number of measurements per station) must be supported

The README says max length 100 bytes, which I suppose we can (?) assume are octets. Also, it mentions that you can assume the station string does not contain the separator ';'.

I guess the station string is also supposed to be free of control characters like newlines, though spaces are allowed. This, however, is not stated.