Up Down counter

#define UP   2
#define DOWN 3
int counter1 = 5;
int counter2 = 4;

int upDown(int &val, int inc, int max=9, int min=0){
  if (val != min)
    val = (val + inc) % (max +1);
  else if(inc > 0)
         val = (val + inc);
}

void setup() {
  Serial.begin(9600);
  pinMode(UP,   INPUT_PULLUP);
  pinMode(DOWN, INPUT_PULLUP);
}


void loop() {

  if(digitalRead(UP) == LOW){
    upDown(counter1, +1);
    Serial.print("\nCounter1: ");
    Serial.println(counter1);

    upDown(counter2, +2, 20, -4);
    Serial.print("Counter2: ");
    Serial.println(counter2);
    delay(200);
  }

  if(digitalRead(DOWN) == LOW){
    upDown(counter1, -1);
    Serial.print("\nCounter1: ");
    Serial.println(counter1);

    upDown(counter2, -1, 20, -4);
    Serial.print("Counter2: ");
    Serial.println(counter2);
    delay(200);
  }

}