Hello everyone. The baby has greenish stools, the pediatrician said he…

Hello everyone. The baby has greenish stools, the pediatrician said he should only poop yellow (baby is 1.5 months old). The pediatrician prescribed us Rotabiotik Baby one packet per day and didn't explain how to give it. I found online that in 100 ml of water dissolve... Is 100ml too much? Today I wanted to give him but he doesn't drink only 20-30 ml, he drank and didn't want more. What should I do or force him to drink the whole liquid (100ml)?