The importance of the RCI is in determining whether this child's relative standing compared to his peers has changed between the first and second administration. If the RCI is not significantly different, it means his growth relative to his peers has been relatively similar. If he was behind before, he has not caught up. If he was ahead, he has maintained that lead. In this case, even though the RCI is considered not significant, it is still negative, so it means that, although his rate of growth has been a bit slower than that of his peers, it is only somewhat slower, not enormously slower. (The conventional RCI cutoff for significance is an arbitrary number; I've seen numbers from 1.645 to 1.96. Even if his RCI is below that cutoff, it still means something.)
