Bug of the maximum. We are playing with the 5030 online with the MCS
See the attached max-error.jpg attached image
The red ▼ max marker shows: 389.44nT @ 0.063 kHz
But this is not true: from result window we know that the maximum is 434.3nT @ 0.045kHz
What are we doing wrong?

This looks like a NF-5030 with 30MHz expansion which does NOT work below 1kHz (see datasheet) so you are just measuring within a frequency range the unit does not support. Also see posting viewtopic.php?f=31&t=518&p=857&hilit=30mhz#p857

BTW: Please note that the Power-Setup (Hotkey 2) is ONLY valid for 50Hz and 60Hz signals. For all other signals use multiple of 15Hz as noted in the manual or you can create unwanted images.
E.g. to measure a 45Hz signal change the start frequency to 30Hz and the stop frequency to 60GHz and it should work perfect.