Thanks for your reply about (Don’t sure do I have a fake ledger nano s or not).
When I have received the ledger nano s from ebay, I entered my own pin and the device generate the 24 words. so am I save and dont need to reset the device etc. (Because I must contact some ICOs to change the ETH wallet etc. and I hade already changed once when I become the ledger nao s, so to ask them again to chnage the wallet will not be nice)