What is the axis rate?

Hi,

What is the axis rate? I attached Mouse-X axis to one of the function where I acumulate the total axis rate:

InputComponent->BindAxis("Turn", this, &AMyPlayerController::Turn);

and the Turn function:

void AMyPlayerController::Turn(float Val)
{
	Total += Val;
	UE_LOG(LogTest, Log, TEXT("Turning: %f"), Total);
}

And when I turn I see that this Total is not actual rotation value but rather somehting else. When I turn 90degress the total is 180, so it always rotation * 2.
So what does it actually mean?

Thanks