Well, is turning into a twenty foot tall, nine tailed giant, with a deep resonating voice spacious, cat?
Using Hakuno as a comparison, Amaterasu is WAY taller than 20 feet. Hard to judge due to perspective, but if you just compare by sight and not think about perspective nor distance, Hakuno is the size of Amaterasu's hand, but if you add in perspective and distance, Hakuno is easily smaller than Amaterasu's pinkie finger.
