Arduino 23 Stepper motor issues.

I recently made a soda can crusher that requires 24,000 steps in each direction to crush the can. When I use a number greater then 20,000 steps it goes in the wrong direction. Is there a way to fix this? Here is the code. Also I want the motor to turn off after each use.

/*
 Can Crusher code #2
 */
 #include <Stepper.h>
 // NEMA-23 Motor with DM542T Controller
 const int STEPS_PER_ROTATION= 800; //800 Steps per full rotation

 // DM542T Stepper Controller pinouts
const int INPUT1 =2; //PUL+ To Digital pin 2
const int INPUT2 =3; //PUL- To Digital pin 3
const int INPUT3 =4; //DIR+ To Digital pin 4
const int INPUT4 =5; //DIR- To Digital pin 5
const int INPUT5 = 6; //ENA- To Digital pin 6
const int Input6 = 7; //ENA+ To Digital pin 7

//Initialize the stepper library to stepper motor controller
Stepper myStepper(STEPS_PER_ROTATION, INPUT1, INPUT2, INPUT3, INPUT4);


void setup() { 
  // put your setup code here, to run once:
myStepper.setSpeed(300); // Default speed 300 RPM
// Set the rotation
myStepper.step(20000);
 //Set Delay for 2 Second
//  delay(2000);

 // put your setup code here, to run once:
myStepper.setSpeed(300); // Default speed 300 RPM
// Set the rotation
myStepper.step(4000);
 delay(2000);
  // Set return on motor
myStepper.setSpeed(300); // Default speed 300 RPM
// Set the rotation
 myStepper.step(-20000);

// Set return on motor
myStepper.setSpeed(300); // Default speed 300 RPM
// Set the rotation
myStepper.step(-4000);
delay(2000);
pinMode(6,OUTPUT);
pinMode(7,OUTPUT);
  digitalWrite(6,LOW); //Turn off Motor
  digitalWrite(7,HIGH); //Turn off Motor
 while(1){}
}

void loop() {

  // put your main code here, to run repeatedly:
    // put your setup code here, to run once:
//myStepper.setSpeed(20); // Default speed 20 RPM
// Set the rotation
//myStepper.step(500);
 //Set Delay for 1 Second
// delay(2000);

}