Contapezzi con display 7 segment

Ok sono riuscito nel mio intento, contare fino a 90, ma per curiosità ho provato a inserire anche la variabile per le centinaia in modo da poter contare anche oltre il 99, ma al nr. 100 appare la scritta 1a0 e a 110 appare 1b0 e così via senza però visualizzare 100...110...120... Cosa c'è di sbagliato?

 //State change detection (edge detection)
//We always have to include the library
#include "LedControl.h"

/*
 Now we need a LedControl to work with.
 pin 12 is connected to the DataIn 
 pin 11 is connected to the CLK 
 pin 10 is connected to LOAD 
 We have only a single MAX72XX.
 */
LedControl lc=LedControl(12,11,10,1);

/*  The circuit:
 - buttonpin attached to pin 2 from +5V
 - buttonreset attached to pin 4 from +5V
 - 10 kilohm resistor attached to pin 2&4 from ground
*/
// this constant won't change:
const int  buttonPin = 2;// the pin that the pushbutton is attached to
const int  buttonReset = 4;// the pin that the buttonreset is attached to

// Variables will change:
int contatore = 0;   // counter for the number of button presses
int buttonState = 0;         // current state of the button
int lastButtonState = 0;     // previous state of the button
int unita = 0;
int decine = 0;
int centinaia = 0;

void setup(){
  /*
   The MAX72XX is in power-saving mode on startup,
   we have to do a wakeup call
   */
  lc.shutdown(0,false);
  /* Set the brightness to a medium values */
  lc.setIntensity(0,8);
  /* and clear the display */
  lc.clearDisplay(0);

  // initialize the button pin as a input:
  pinMode(buttonPin, INPUT);
  pinMode(buttonReset, INPUT);
}

void loop() {
  // read the pushbutton input pin:
  buttonState = digitalRead(buttonPin);

  // compare the buttonState to its previous state
  if (buttonState != lastButtonState) {
    // if the state has changed, increment the counter
    if (buttonState == HIGH) {
      // if the current state is HIGH then the button went from off to on:
      contatore++;
 unita=contatore%10;
 decine=contatore/10;
 centinaia=contatore/100;
 
      lc.setDigit(0,2,(byte)centinaia,false);
      lc.setDigit(0,1,(byte)decine,false);
      lc.setDigit(0,0,(byte)unita,false);
    } 
    // Delay a little bit to avoid bouncing
    delay(50);
  }
  // save the current state as the last state, for next time through the loop
  lastButtonState = buttonState;

  // if the buttonreset is pressed reset the buttonpushcounter
  if  (digitalRead(buttonReset) == HIGH){
      (contatore = 0);
       lc.clearDisplay(0);
    }
  }