A silly idea comes out of your head and you say Human, after all humans don't have tails and you don't think this machine can really grant wishes anyways. You think this is all just a scam, you could not be any more wrong.
The Machine hears your request and it vaporizes your clothes but leaves your body intact and unharmed and it pulls out mirrors, so you can see all of you, first your testicles go up into your belly region and become Ovaries, your Vas Deferens, Fallopian Tubes, Prostate Uterus, or Womb, and your penis and scrotum become a clitoris , urethral meatus, labia majora, labia minora and vagina, they are all just below and in front of your now female human anus, your female navel or bellybutton or belly button is exposed and naked, YIKES, you are naked you try to cover yourself with your hands but you can't move only see your body changing.
Lastly you feel pain coming out of your upper butt just above your asshole, it feels painful like a combination of someone pulling on your tailbone, trying to yank it, your spine and your back, and what it feels like to poop when you have constipation, you feel and see in the mirrors your tailbone unfusing, penetrating the skin of your lower back and upper butt just above above your naked human girl butthole and it is bony and has many vertebrae, it grows to be about 174 cm long then it suddenly stops, it grows muscles around the new vertebrae, and skin grows around the new muscles, however the skin does not grow hair, you now have a naked hairless bareskin human tail just above your pucker.
You wiggle your new human tail to see if you can control it and you feel and see in the mirrors that you can and that it is undoubtedly yours and it belongs on your body. When you try to pull it, you feel pain as if pulling it feels like you are trying to pull out your vertebrate, spine, and spinal cord out of your butt, if your tail gets cut off, you will die, This is all too real.
A sudden realization dawns on you, what if somebody sees you like this, you might be in a freak show, a circus, a zoo, a lab as a specimen or worse, you have got to get out of here and find a way to hide your 174 cm long human tail before anyone sees you are a human with a tail coming out of your butt, you also consider your tail to be a private part too.