Dataflash log compass interference practical meaning and units

Hi all,

I am trying to review how well my drone is laid out by looking at the magnetic interference. I have plotted mag_field using

mag_field = sqrt(MagX^2, MagY^2, MagZ^2).

It says to use this formula to calculate mag-field length, which I am assuming is mag_field, but what do these values actually indicate? what is mag-field length/mag_field ? and what are the units of mag_field?

I have attached my plotted data in Matlab below: