Keypad showing wrong value on serial monitor with Arduino

When I press A from keypad it call the function shahbaz , then I enter some value from keypad which multiply with int a and show results on seven segment .but show no results on seven segment display. When I print this result on serial. Monitor. it show wrong answer like(-960, 000).seven segment display show 0000 when I tried to multiply the value with keypad value it show wrong answer . if i type t=1200*20 ; no value enter from keypad it show wright answer on serial monitor and seven segment display

 #include <Keypad.h>
 #include "LedControl.h"
LedControl lc = LedControl(11,3,4,1); //DIN, SCK, LOAD,1xMAX7219
int a=20;
int b=30;
int c=37;
int d=40;


const byte ROWS = 4; 
const byte COLS = 4; 

char hexaKeys[ROWS][COLS] = {
  {'1', '2', '3', 'A'},
  {'4', '5', '6', 'B'},
  {'7', '8', '9', 'C'},
  {'*', '0', '#', 'D'}
};

byte rowPins[ROWS] = { A0, A1, A2, A3}; 
byte colPins[COLS] = { A4, 5, 6, 7}; 

Keypad customKeypad = Keypad(makeKeymap(hexaKeys), rowPins, colPins, ROWS, COLS); 

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
//  inputString.reserve(10);
  lc.shutdown(0,false);  // Wake up the display
  lc.setIntensity(0,7);
   //lc2.setIntensity(0,7);// Set Brightness 0-15
  lc.clearDisplay(0);  // Clear display
}

void loop() {
  // put your main code here, to run repeatedly:
    char customKey = customKeypad.getKey();
    customKey=customKey-'0';

    if(customKey=='A'){// when press it go to function shahbaz.
      shahbaz();
      }

}





void shahbaz(){
  
  
  
  
 char customKey = customKeypad.getKey();
 customKey=customKey-'0';
    long  int t=a*customKey;
      
      Serial.print(t);
      
      Serial.print(customKey);
       long   int t=customKey*a; // here get value from keypad and multiply with value of //int a but it show nothing when i print this value on serial monitor it show -960 

  int digitOne =    (t%10);
    int digitTwo =    (t/10)%10;
      int digitThree =  (t/100)%10;
      int digitFour =   (t/1000)%10;
      int digitFive =   (t/10000)%10;
      int digitSix =    (t/100000)%10;
      int digitSeven=   (t/1000000)%10;
      int digitEight =  (t/10000000)%10;


    //MSB digitEight, LSB digitOne

      lc.setDigit(0,7,digitEight,false);

      lc.setDigit(0,6,digitSeven,false);

      lc.setDigit(0,5,digitSix,false);

      lc.setDigit(0,4,digitFive,false);

      lc.setDigit(0,3,digitFour,false);

      lc.setDigit(0,2,digitThree,false);

      lc.setDigit(0,1,digitTwo,false);


      lc.setDigit(0,0,digitOne,false);
      delay(1000);

  }