Error reading peak signal values

When I apply 142mV (100mV rms) from the internal signal generator to Ch A I do measure:
Amplitude at peak: -20.69 dBV
Average amplitude at peak: 74.2mV

Why do I read 74.2mV and not 92.4mV that is equal to -20.69 dBV?
And why not 100mV or 142mV (peak value)?

According to the Picoscope 6 users guide (Spectrum measurements):

Amplitude at peak.
The amplitude of the peak signal value.

Average amplitude at peak.
The amplitude of the peak signal value averaged over a number of captures.

In other words: "Average amplitude at peak" should be equal to "Amplitude at peak" when the stddev is close to zero..


PicoScope® 6 - PC Oscilloscope software version: 6.6.23.2
Copyright © 1995-2012, Pico Technology Ltd
Model: PicoScope 4262

We are currently looking at the Picoscope 6 measurements for the 4262 as there may be a few inaccuracies with these.