Breastfeeding after work?

Emma

I went back to work this week part time, 4 hours a day. Baby is staying with my MIL. He's getting a bottle of pumped milk while he's there. Today he pretty much finished the bottle(it had 6oz, I'm gone technically 5hrs due to travel). When we got home he nursed for almost an hour! I'm wondering if he is comfort nursing, or if I should be asking her to try and get him to eat more while he's there. ATM she is feeding him on demand.