Z auto-align question

Trying to set up Z auto-align for the first time on a 320x320mm bed with a usable 300x300mm area. Could someone interpret what the positions are on the following statements? Thanks.

#define Z_STEPPER_ALIGN_X { 10, 150, 290 }

#define Z_STEPPER_ALIGN_Y { 290, 10, 290 }