This is probably simple, but I cannot see it. Problem states shape to 384K. But results of the config show:
shape average 384000 7680
why the 7680 Bc ? What not just: shape average 384000
dont really think that you are wrong in what you did because it doesnt specify. if you go by the lab before the one in question it specifies a tc of 20ms which gives you the 7680.