This is just a very fast way to get the three flasks of liquid to make medicine in the third chapter for anyone having difficulty visualizing the steps to get the right measurements (i.e. people like me that are bad with numbers), since the game is brand new and no walkthroughs are available yet.

There are probably other ways to go about this puzzle, so this just shows one way to get it done.

Fill the 9 flask and empty it into the 4 flask. Empty the 4 flask.
Repeat this until you have 1 unit of liquid in the 4 flask. Leave it there.

Now fill the 9 flask again and repeat the same process, and you'll be left with 2 units of liquid in the 4 flask. Once again, leave them there.

Fill the 9 flask again and empty it into the 4 flask, then empty the 4 flask. Repeat this until you have three units of liquid in the 9 flask, then pour the three units into the potion pot.

tart by filling the 9 flask with green liquid, then empty it into the 4 flask. Empty the 4 flask.
Repeat until you have one unit in 4 (same as with the red previousl). Leave it there.
Now fill the 9 and empty it into the 4 again.
You'll be left with 6 units in the 9 flask which can be emptied into the potion pot.

Fill the 4 flask and empty into the 9 flask. Repeat this three times and you'll have a full 9 flask and 3 units in the 4 flask.
Empty the 9 flask.
Pour your three units from the 4 flask into the 9 flask.
Refill the 4 flask and empty it into the 9 flask.
You'll have a total of 7 units and can empty it into the potion pot.