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.