............ but what does the IJ mode mean?
G90.1 & G91.1 Set IJK Arc Mode
Interpretation of the IJK values in G02 and G03 codes can be in one of two distance modes: absolute or incremental.
To go into absolute IJ mode, program G90.1. In absolute distance mode, IJK numbers represent absolute positions in terms of the currently active coordinate system.
To go into incremental IJ mode, program G91.1. In incremental distance mode, IJK numbers usually represent increments from the current controlled point.
Incorrect settings of this mode will generally result in large incorrectly oriented arcs in the toolpath display.