I am using PicoScope 6 with 4262.

As shown in the picture, the real-time AC RMS measurement result is 1.331mV, while the AC RMS of the same waveform saved as psdata is 3.514mV. I also save data as .csv and calculate with excel. The result is also 3.514mV, the same as the one saved as psdata. So is the real-time AC RMS measurement incorrect?