A Picture for a Certificate

I needed a picture for my certificate. My husband told me that the easiest way is to take a picture with my iPhone, send the data to a 7-Eleven machine, and print it out. According to him, at the end of the program, a number is given at the end of the procedure, and I just punch in that number into the machine at the store. He was helping me before going to work, but it was getting late, so he left home before explaining me enough. After he left, I tried it by myself. I took my picture, downloaded the program, and went through the process. I had expected to see the number in the end, but I was given a QR cord.  Luckily, a 7-Eleven is located only a few minutes away, so I went there with my iPhone. After placing the QR code over the machine, I pressed the button of sending data on my iPhone and my picture appeared on the machine's screen. It said the fee was 250 yen. I didn't have any coins, so I looked for the place to insert a bill. I went to the cashier to ask where I could insert a bill. She said only coins were available on the machine. She exchanged a 1,000-yen bill for a 500-yen coin and five 100-yen coins. I went back to the machine and put three 100-yen coins. I got a sheet of four certificate picture successfully. I had to push the button to get back 50 yen. However, I got 450 yen. I thought the machine made a mistake or someone who used the machine before me left the change. I almost went back to the cashier to tell that.  In a short while, I realized that I had put in a 500-yen coin and two 100-yen coins by accident.  I was relieved that I didn't say anything to the cashier.  When my husband came back home, I told him that I had successfully printed out the picture at 7-Eleven and that I thought the machine had made a mistake with a change. He laughed a lot and said, "The machine is much smarter than you!"