Do they happen to make this kind of sales, too?
I once had a chance to tell our local pub that their Chinese New Year sale sign is incorrect. They decided to put the sign in Chinese but got confused over how the discount is written in Chinese, so they wrote a price of +50% instead of -15%.
but why?
In Chinese the sale price is stated as the remaining part of the original, and it is written in tens of percents (折), so the full price is 10折, and 15% discount is 8.5折, but they had a sign of 15折. Google translate seems to think 15折 = 8.5折 but I would guess that it's just AI outsmarting itself again. Now, a real person would probably be able to guess what was meant anyway, but it's nice to write things correctly and not rely on guesswork