24oz would be much more than the recommended range. I'm wondering why baby was offered 8oz of milk at once? It seems like a recipe for overfeeding to me.
I can see why mom is concerned. A lot of moms don't make quite what baby needs at daycare. I always had to pump an extra session before I went to bed or in the morning in order to keep up (especially around 4-8 months)
https://kellymom.com/bf/pumpingmoms/pumping/milkcalc/