There is no danger here. Erasing codes not only delete the generic OBD II codes stored in the vehicle ECU, but also the codes defined by your vehicle manufacturer. Some freeze frame data will also be deleted. This notice is for you to consider carefully to do the erasing codes. Because sometimes erasing codes can't fix your problem, you may need to take the car to a workshop then if the codes still saving in the ECU, it is better understandable for the mechanics to find out what occured in your car. For an ordinary user, when your car got into some kind of troubles, you would like to check if you can fix it by yourself. So you scan the car, read the codes and try to fix it, and you believe you did fix it, then you will want to erase the codes to see if you had fixed it successfully.