The question is: is your puppy lean or chunky? The amount fed doesn't seem like it's enough for a growing puppy that age, but you have to look at the pup first. If your pup is lean, she's probably not getting enough to eat and is very hungry.
The concept that feeding too much will cause soft stool is very misleading. The feeding too much thing has more to do with the dog getting way too many calories and/or way too much fat and/or fiber and that's why they get the soft stool. Your pup needs so many calories a day, period, and you have to get them into her or she will be extremely hungry. If your pup is getting soft stool from eating enough to maintain her growing, lean, body, then there's a problem with your pup with the dog food itself or the fat or the fiber content.
Elaine and the herd