Binary counting using 12 LEDs

Using Arduino Programming Questions
34

spatula:
Guess what the ASCII value of '9' is? 57. In

 sum=firstKey+secondKey;

you are adding the characters ('0'..'9'), not the numbers (0..9).

You are right.
I managed to do the code for addition.

#include <Keypad.h>

int ledPin[12]={13,12,11,10,9,8,7,6,5,4,3,2};
int number1=0;
int number2=0;
int keyPressed=0;
int counter=0;
int sum=0;
char firstKey;
char secondKey;
long previousMillis = 0;
long interval = 1000;

const byte ROWS = 4; //four rows
const byte COLS = 3; //three columns
char keys[ROWS][COLS] = {
	{'1','2','3'},
	{'4','5','6'},
	{'7','8','9'},
	{'*','0','#'}
};
	

byte rowPins[ROWS] = {31, 33, 35, 37}; //connect to the row pinouts of the keypad
byte colPins[COLS] = {39, 41, 43}; //connect to the column pinouts of the keypad
	
Keypad customKeypad = Keypad( makeKeymap(keys), rowPins, colPins, ROWS, COLS );

void setup(){
  Serial.begin(9600);
  
   for(counter=0; counter<12; counter++)
   {  
  pinMode(ledPin[counter], OUTPUT);      // sets the digital pins as output
   }
}

void loop(){
  
  char key = customKeypad.getKey();
  /*if (key) {
    Serial.println(key);
  }*/
  if (key) { // blocking from anything not needed
   keyPressed= keyPressed+1;
   if (key != '*' && key !='#'){
    
  // number =key - '0' ; // convert key to its value
  } // end of sort
   if (keyPressed ==1){
     number1= key - '0';
     firstKey=key;
   }
  else if ( keyPressed==2){
    number2= key - '0';
    secondKey=key;
    sum=(number1 *10)+number2;
  Serial.println(sum);
 
  //Serial.println(number); 
  if (sum){
    char key = customKeypad.getKey();
    // I'm not sure about this loop
    
    if (key == '#') // increment binary counter
    {
       Serial.println("i"+firstKey);
       //digitalWrite(13, HIGH);
       //delay (1000);
     for(counter=0; counter< sum; counter++){
      //digitalWrite(ledPin[counter-1], HIGH);
      digitalWrite(ledPin[counter], HIGH);
       unsigned long currentMillis = millis();
       if(currentMillis - previousMillis > interval) {
        previousMillis = currentMillis;
      } // end of millis
     
      
     } // end of increment counter
    } // end of '#'
    
    
    else if (key == '*') // decrement binary counter
    {
      for(counter; counter < sum; counter-- ){
        if (counter < 0) counter = 0; // checks to see if
        // counter does past zero then set it back to zero
      digitalWrite(ledPin[counter], LOW);
      unsigned long currentMillis = millis();
      if(currentMillis - previousMillis > interval) {
        previousMillis = currentMillis;
      } // end of millis
     
      } // end of decrement counter
      
    } // end of '*'
    } // end of sum
    keyPressed=0;
   } // end of keycount
  } //end of if(key)
   
 } // end of loop

Now, when I press two numbers I get the right sum on the serial monitor.
However, if I press '*' I get minus 6. Similarly, for '#' I get minus 13.
How do I convert the third key to either increase the decrease the counting?
At the moment my LEDs don't do anything.
I also have to convert the input to binary counting.
How do I do it?
Regards