How big a mess?

On the way home from the store today Emma kept picking at her brother. She'd bug him, he'd smack her, she'd bug him again. It was driving me crazy. Finally I said, "Emma, if I have to tell you one more time to leave your brother alone then when we get home I am going to make you clean up Aaron's whole room!". It got quiet so I snuck a glance in the rear view mirror. Emma was keeping her hands to herself but she kept glaring at her brother. I saw her give him one huge stink eye look and then she said, "Mom, how big a mess is Aaron's room?".