Is this enough formula?

My 9 week old is only drinking 18-20oz average per day with good days up to 25oz but yesterday only 16.5oz. She drinks 3 to 5oz every 4 hours but sleeps up to 12hours at night so would she be getting enough milk in a 24 hour day? I make 6oz bottles but like I said sometimes she’ll only take 3oz and has never wanted more past 6oz.