Bottle feeding 5 months

Gail

My 5 months old take 3 naps so i can only fit 4 feedings (6-6.5oz max per bottle) in a day. So it is like 24oz a day. Her ped said to do 28 oz but cant seem to fit an extra feeding in. Cant increase her oz per feeding, she wont take it. How are you moms doing it or what do you suggest?