When setting the brightness value of a light via the API call /api/HomeAutomation.ZWave/{id}/Basic.Set/{value}, the value is in the range of 0-100, that is translated into the appropriate level for ZWave, but is sent unchanged through to HG. This results in UI anomalies where the UI is showing levels 100 times the specified value -- e.g. /api/HomeAutomation.ZWave/1/Basic.Set/50 will set the ZWave to 50%, but reported watt usage will be 50 times, not 50%.
