Re: How to start levelling from scratch?

OK, I think that I have all necessary changes made, but unsure of the following:

#if ENABLED(AUTO_BED_LEVELING_3POINT) || ENABLED(AUTO_BED_LEVELING_UBL)
#define PROBE_PT_1_X 80
#define PROBE_PT_1_Y 80
#define PROBE_PT_2_X 250
#define PROBE_PT_2_Y 80
#define PROBE_PT_3_X 250
#define PROBE_PT_3_Y 210

I have not been comfortable identifying these probe point coordinates. Example:
#define PROBE_PT_1_X 80
#define PROBE_PT_1_Y 80
Will this direct the probe to travel to X80 Y80? From what point, X0 Y0?
And then:
#define PROBE_PT_2_X 250
#define PROBE_PT_2_Y 80
Also from the same X0 Y0?

With the current Configuration.h settings, when I send G0 X0 Y0, the Probe goes to (approximately) X32 Y60 (as measured from the front left corner of the glass bed.
G28 sends all to HOME positions.

How do I get a print to start at center of bed? Adding a script to my slicer?

Thanks for your help.