Gave baby one extra ounce of water

Hi All, we accidentally gave our 5 week old one extra ounce of water to formula for one feed. Is this something to be concerned about? The pediatrician line we called said to monitor a few symptoms like lethargy and twitching but honestly he does that to some degree normally. Should we take him to the ER? We would hate to expose him being immunocompromised at his age. Would love to hear your thoughts. Thank you for your help in advance!