Signal in iwinfo command

Sometimes, the SSID may not be detected due to a
failure of the rf function on the wireless AP.

I would like to check the actual strength of the rf
through statistics to determine if the rf function is faulty.

Therefore, I checked the signal value through the "iwinfo" command,
and I would like to know what this means.
(Ex: signal: -44dBm)

Is the actual measurement of the rf that I sent correct?