How to skip the first line and output the second?
IF and only IF you want exactly what you have asked for which is alternate lines not to be output then this is a very crude and quick solution.

Outside of loop() add this declaration:

bool skipNextLine = true;  // true skips the odd lines, false skips even lines


And change the end of your code like this:

  if (EncVariation != 0) {
    encoder0Pos = encoder0Pos + EncVariation;
    int degrees = (encoder0Pos * 6) % 360 ;
    if(degrees&lt;0){ deg = 360 + degs; }
    if (!skipNextLine)
    {  // This will skip alternate lines
        Serial.println (deg);
        skipNextLine = true;
    }
    else
    {
        skipNextLine = false;
    }
  }