Numerical range for homematic signals

If I get it right, the standard range for signal strength is 0 to 4 (the icon has 4 bars). Some devices (netatmo?) seem to have a maximum of 5 (perhaps unless you map the lowest to 0).
How about homematic devices (e.g. motion detectors etc.)? It seems they use (or are mapped via homegear and binding) a range from 0 to 4, but I failed to find any definitive documentation on this.
BTW: most other attributes (like CAPTURE_WITHIN_INTERVAL) sometimes appear in threads, but there as well I failed to find some comprehensive documentation.
Any pointers appreciated.