sending multiple values in port.write in processing

Using Arduino Interfacing w/ Software on the Computer
7 
      if (Serial.available() > 0) { //  Check if there is a new message
      dirA= Serial.read();    //  Put the serial input into the message
      dirB= Serial.read();    //  Put the serial input into the message
      pwmMotorA = Serial.read();
      pwmMotorB = Serial.read();
      }

Suppose Serial.available() returns 2, as in there are 2 bytes in the serial input buffer. What is going to happen when you try to read the 3rd and 4th values?