Adding my own foods

When I find a food listed on Calorie Count already, I can select it and have the chance to change the quantity.

When I add a food myself, I tag it and when I select it later, I don't get to say how much a serving is or change it. Say that I had a crockpot stew that comes to 140 calories per 3/4 cup serving when I use the tool to add my own foods. Since I have leftovers, I tag it so I can just choose it again tomorrow. But tomorrow I'm eating 1 cup. Right now, I just change the calories (which doesn't change anything else like fat or fiber.) And it doesn't tell me what a serving is (eg. 1 cup, 1/2 cup).

Is there something I'm missing? Is there a way to have the serving size stick with the entry other than in the comments when I tag it? Is there a way to make it dynamic so I can change the serving size for my current meal?