Both my children only ate 3-4oz of breastmilk at a time from about 4-12 months. When they were younger, I'd send 4 3oz bottles and as they got older I sent 3 4oz bottles. I had to pump 3x at work and once before I went to bed in order to make this happen.
I don't want to assume, but around that age it starts to become hard to pump more than that. Especially if mom is only pumping at work.
I always relied on this resource to help me plan my bottles.
https://kellymom.com/bf/pumpingmoms/pumping/milkcalc/