If you cook a stew, eat any of it, but not all (1/4, 1/2, 3/4) and than create 4 bowls of stew the stew bowls will actually divide the original stew value and not the current one.
For example if you make a stew with with 100 hunger and eat half ---> cooking pot of stew now has a hunger value of 50.
Now if you make 4 bowls of stew each bowl will have a hunger value of 25, instead of 50/4 = 12.5.
I haven't tested if the same happens for soup but it might just be the case. I just always cook stew in my game :D.
This might be a duplicate but I couldn't find another post about it.