The value you see is based on many factors. The received signal includes all information in the environment (FoV). That value depends on the gain of the transmitter-receiver antenna, RCS, distance of targets, amplifier.... you can research some radar equations. In addition, it is also affected by processing processes like windowing, zero-padding...etc. In my opinion, hard to say whether it is the expected value or not. However, if you ignore some theory and just observe that signal like a vector of numbers. You can find some local maxima values in this vector, some of these values represent your targets and if you design an appropriate threshold you can define what is the desired target and what is the noise.
In radar GUI you can see their scale is dBFS, and if correct, human signal strength is -50dB, -60dB around 1-5meter, and it is good. It is hard to observe when you stay in a room with many obstacles, may you need to apply subtraction(MTI) on your signal to make it clear (but the signal's strength is significant change). The characteristic of FMCW allows us to remove obstacles by subtraction and it is an important algorithm.
