Haircut

I got a haircut today, and when I paid, the girl gave me a receipt. 'It's also a three-week warranty', she said with a smile.
What does a haircut warranty mean, exactly? Do I get my money back if the shampoo she used makes my hair fall out? Or maybe if my girlfriend bursts out laughing when I show her the new 'do, I get a full refund?
I have a good mind to go back tomorrow. 'Hi, I was here yesterday. I'm not satisfied with my haircut. I want my old haircut back. You know, with the long hair?'