How small?

Karyn returned a few minutes later wearing a slutty nurse costume.
"Where did you get that outfit?" John asked as she approached him.
"It's my Halloween costume from last year, I figured it would be appropriate for what we're about to do", Karyn replied as she bent over John, giving him a nice view of her breasts. They were proportionately smaller than the ones he now had but at his reduced size they were the biggest he had ever seen. Instead of the usual tightening in he underwear he normally felt, he suddenly felt very warm down there. The feeling was much more intense than normal but he was able to keep it under control for now.
Karyn stood him up and raised his arms over his head so she could remove his top. It was tight but she managed to peel it off with no trouble, causing both breasts to bounce when they came free. This caused John to wince which she noticed and said, "Aw, poor baby. Nurse Karyn will kiss it all better" and she gently lifted his right breast and began massaging the nipple with her tongue. The feeling he had before suddenly became too much for him and he let out a shriek or pleasure. This startled Karyn who laughed and said, "See, I told you you would enjoy this. Now to get to business. Stand straight up"
John did as he was told. Standing on the desk he was about a foot taller than Karyn, who looked up at him and said, "This won't do" and added, "I wish you were about 1/3 smaller". As John opened his mouth to protest he knew it was too late. He could feel the desk expanding underneath him and saw Karyn's head rising until he was eye level with her mouth. Before he could say anything, she pressed her finger to her lips and said, "Shhh. I'm busy", as she pulled out a tape measure and held one end at his feet and one at his head. Looking to the side he would see the number 34 and knew that wasn't good. Karyn picked up a pen and wrote on a clipboard that was part of the costume while speaking it out loud, "Height: 37 inches"
"37 inches!" John yelled, his voice even higher now, "What are you doing to me Karyn? I can't live like this! I'm not even a midget anymore, I'm a freak!"
Karyn looked down and patting him on the head, replied "Don't you worry your pretty little head, Nurse Karyn will take care of you. Now, next up we need to get your measurements, please disrobe and hold out your arms.
John just stared up at her in disbelief.