Signal Range in the CAPsMAN Access List means TX Signal or RX Signal or RSSI ?
RX Signal
Does RX SIGNAL mean the signal strength from the client device(phone,notebook…) to the AP?
It is the signal strength of the client, measured on the CAP.
Think here you can find some good (additional) information:
https://help.mikrotik.com/docs/display/ROS/CAPsMAN