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 }

First, I don't know what version of Marlin you're using, but official 2.0.x uses:

#define Z_STEPPER_ALIGN_XY { {  10, 190 }, { 100,  10 }, { 190, 190 } }

Those determine the positions on the bed that will be probed to try to align the bed. If you only have 2 Z motors you should remove the last pair of numbers:

#define Z_STEPPER_ALIGN_XY { {  10, 190 }, { 100,  10 } }

If you have three Z drivers the points should be on a line between the center of the bed and a motor (or even better right above the motor).

An example for your setup might be:

#define Z_STEPPER_ALIGN_XY { {  30, 150 }, { 270, 150 } }

for two motors.