Overfed?

mcp0805

Today was my first day back to work and my in laws are watching LO. I left 5 bottles 4 oz each which was enough for every 2 hours and I thought plenty. MIL fed her all of that as well as 4 oz I had pumped for tomorrow. Did I underestimate how much she would need or was she overfed?  Would you leave 6 bottles with a little less or just 5?  At this rate I won't be able to keep up with her pumping.