First, am I correct that dB in the WSPR data window is the audio SNR for the received signal within a 2.5 KHz window?

For some strong signals with quite high dB readings, I am able view their audio and RF on a spectrum analyzer. I have seen strong signals which maintain at least 2O dB above the average noise for the full 2 minute cycle yet those same signals only get reported with plus 3 or 4 dB. Clearly I am only able to "see" signals above the noise level.

What am I missing?