Hi... don't worry it's not an extremely dangerous thing to do , but chances are that your baby will be extremely constipated if there's more formula to water ratio . Or sometimes he may not react at all. But it may be a health issue later if You do very often . So it's best to adhere to the Instructions on the tin.
Nothing to worry about as its a one off mistake but I would say an upset stomach at the most but maybe even nothing.
Dont worry.probably a bit constipated.no big issue. And follow with lots of fluid if worry about constipation.
Think it's fine... give him more water ?