If Statement controlling Scale field. Not working.

I think you have more problems than just the formatting issue. Audio levels typically run from 0 to 30. Four is a very low threshold for most audio and the change from 100 to 104 isn't much so you are not going to get much of a reaction.

Another problem is that a simple if statement is on or off. Your scale would either be 100% or 104%, which is hardly enough of a change to give you much of a change in size unless you just want a small vibration that rattles only when the sound level dips below a very low background noise level.

I would consider using an interpolation method. The first step is to open the Audio Levels Both Channels Slider in the Graph editor set to display a value graph, then look at the range and figure where you want the switch to take place. Then you build your interpolation method.

This tutorial I just released explains it all pretty well.

You need to assign the values to a variable:

if(thisComp.layer("Audio Amplitude").effect("Both Channels")("Slider") < 4){
    x = 102 //' same for 'temp'
}else{
    x = 100 // Same for 'temp'
};
[value[0],x]