If the application is launched standalone (Portable mode), by default it saves data in the same directory of the executable file.
Only if the directory is not writable, it saves data in the user directory as explained above.
You can always control the path with the path options from a command line interface. The value can be a full path, or special values home (for the user directory) or program for the program directory. Examples:
AirVPN.exe path=C:\mydata AirVPN.exe path=home AirVPN.exe path=program