arduino: 2 DIGITAL NUMBERS in LED

led.ino

// Demonstration Arduino sketch for four digit, seven segment display with enclosure
// http://tronixlabs.com/display/led/numeric/four-digit-seven-segment-display-module-and-enclosure/

int latchPin = 13;   // connect to LCK pin
int clockPin = 12;   // connect to CLK pin
int dataPin = 11;    // connect to SDI pin

int i = 0;
int left = 0;
int right = 0;
int sum = 6;
int sumState = 0;
int rest = 5;
int restState = 0;

/*
int LED_SEG_TAB[]={
  0x00, 0x01, 0x02, 0x03, 0x08, 0x09, 0x11, 0x18, 0x19, 0x25, 0x31, 0x39, 0x40, 0x41, 0x48, 0x49, 0x61, 0x63, 0x71,
// 8.   8     0.    0     9.    9     A     9.    9     2     P     º     6.    6     5.    5     E     C     F

  0x83, 0x87, 0x91, 0x98, 0x99, 0xbf, 0xe3, 0xef, 0xf3, 0xfd, 0xfe, 0xff, 0x0c, 0x0d, 0x1a, 0x1b, 0x9e, 0x9f
// U    J     H     4.    4     '     L     _     I     -     .     hutsik 3.   3     7.    7     1.    1
};
*/

int LED_SEG_TAB[] =
{
  0x03, 0x9f, 0x25, 0x0d, 0x99, 0x49, 0x41, 0x1b, 0x01, 0x19
//  0   1     2      3    4     5     6     7     8     9  
};


void setup() 
{
  Serial.begin(9600);
  
  //set pins to output so you can control the shift register
  pinMode(latchPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(dataPin, OUTPUT);

  pinMode(sum, INPUT);
  pinMode(rest, INPUT);
}

void loop() 
{
  sumState = digitalRead(sum);
  restState = digitalRead(rest);
  
  //Serial.println(i);
  if (sumState == HIGH)
  {  
    i++;
    if(i>99)
      i = 99;
  }
  if (restState == HIGH)
  {  
    i--;
    if(i<0)
      i = 0;
  }  

  left = i / 10;
  right = i % 10;
  
  digitalWrite(latchPin, LOW);  
  shiftOut(dataPin, clockPin, LSBFIRST, LED_SEG_TAB[right]);
  shiftOut(dataPin, clockPin, LSBFIRST, LED_SEG_TAB[left]);
  digitalWrite(latchPin, HIGH);

  delay(100);
}