These 3 columns are simply what is returned from the Z-Wave 700 chip's interface to Hubitat.
RTT AVG is the average Return Transit Time from when a command is sent to a device until a response is received. RTT StdDev is the Standard Deviation of the Return Transit Times, and is a measure of how sharp the RTT peak is. A larger StdDev indicates that the RTT vary greatly around the average. LWR RSSI (Last Working Route Received Signal Strength Indicator) is a measure of the signal strength seen along the last working route to the device. Negative numbers indicate that the signal strength is below the noise level; positive numbers indicate that the signal strength is above the noise level.
How to improve them? Well, you can add repeating devices (or simple repeaters) around your house. Or, you can do as many of us have done, and void your Hub's warranty by doing the Lewis Heidrich (@lewis.heidrick) external antenna modification:
