Jim thought about how he was always short for his age. The old man used the balloon to make him taller and even left him an inch taller when he turned him back. Jim actually liked being taller for that brief moment but he was only made taller, and his clothes did not fit him at that moment either. What would it be like if he made himself bigger overall while making his clothes grow with him? What that thought, Jim said, "Control my size and my clothes' size," and blew into the balloon.
With the first breath, Jim felt a little dizzy as he shot up 6 inches in height. At 5'5", Jim was now taller than most of his classmates at school. Before blowing into the balloon again Jim check himself in the mirror and noticed that despite being taller, his proportions remained the same and his clothes grew with him. Satisfied that it worked, Jim blew into the balloon again.
With another breath, Jim shot 6 inches in height to 5'11". As tall as his dad and the height that the old man made him when he demonstrated the balloon to Jim. Despite being as tall as a grown man now, Jim was not satisfied and so blew into the balloon again.
With another breath, Jim shot up 7 inches to become 6'6". As tall as most basketball players. As big as Jim was now, he was not done yet and so took one smaller breath than before.
With that last breath, Jim shot up 6 more inches and became 7 feet tall. With that, Jim took a look around. Everything in his room now seemed so small to him, and the ceiling seemed so much closer. Jim realized that if he stayed this way, he would probably the tallest 12 year old alive. However he would probably be seen as a freak and would never live a normal life. He wanted to be bigger, but this was maybe too big. So Jim eased his grip on the balloon slightly.
Jim's perspective dropped as he began to shrink back down. Jim found it rather fascinating as everything seemed to grow around him. Within about 10 seconds he was back to the height before he used the balloon to get bigger.
"Release." He said when he stopped shrinking. Jim then wondered how he could become bigger without anyone realizing he was bigger than normal.