Serial.write stops working if not used?

Projects Programming
11 
                blank = data[11];//12
                blank = data[12];//13

What does this achieve? You don't use blank.

  while ((Serial1.available() > 0)) {
    for (i=0; i < 15; i++){
    data[i] = Serial1.read();
    }
  }

How about:

  while ((Serial1.available() >= 15)) {
    for (i=0; i < 15; i++){
    data[i] = Serial1.read();
    }
  }