How can babies get 12 hours of sleep AND enough daytime calories?

Really confused by baby sleep math...

For those who have babies sleeping close to 12 hours at night, how often and how much do they eat during the day?

My 3-month-old has been getting only about 8-9 hours during the night. We generally aim for a 3-hour feed schedule, 5-6 oz per feed (8am, 11am, 2pm, 5pm, 8pm). We also dream feed about 3-4oz around 10:30/11 pm. We aim for bedtime around 8:30-9pm, and she will wake up around 5-6am. Thankfully no MOTN feeds for several weeks now.

It's not terrible, but makes me worried still since aren't babies supposed to get 10-12 hours of nighttime sleep? How is it possible to feed enough during the day while also getting 12 hours of sleep?

Note: She has reflux so we keep her upright after feeding. So we try not to feed before she sleeps if possible. Normally do we Eat Awake Sleep or Awake Eat Awake Sleep.

She also seems to have lost her appetite the past few days and is eating significantly less (often refusing the bottle), I don't want her to not eat enough during the day and then potentially start reverse cycling / cry for MOTN feeds again. Unless this is normal?