D.D.
I wouldn't worry about it. Babies eat like crazy during growth spurts, and less in between.
Think of it this way - if you were nursing, you would have no idea how much your baby was taking at each feeding. And as long as she was satisfied when she was done, you'd consider it a successful feeding. Try to see it that way with a bottle too, and as long as she is happy, energetic, and having a wet diapers, don't worry about counting ounces.