How much should I be feeding my kitten?

Hi,
I'm a new cat owner and have a gorgeous 19 week old kitten. She weighs 1.7kg (nearly 1.8) which the vet said is an ideal weight for her and that her body condition is great. We follow the guidelines on the food we give her and for her weight it says to give 20g 3 times a day but I'm not sure this is enough? She eats it all and seems to be constantly hungry and looking for food? I don't want to over feed but I don't want to under feed either!
Can anyone help?
Thanks

I personally always keep kibbles out for my cats to eat. Specially for kittens it's important they get enough food to grow into strong adults. If you decide to do this, make sure you keep an eye on her weight as you do not want her to become obese, but for me personally it hasn't happened yet and they are both nearly 2 years old. My cattery told me to do it this way and she doesn't have obese cats either, so it's possible to do it for even longer than just 2 years.

My vet had me free feed all my cats until they were a year old. Then after a year she told me to give them 3-4 small meals a day.  I do give them wet 3 times a day, but I still leave dry out because I have an older boy who I can not get to love wet food.  He picks at it.  None of my cats are overweight and are all healthy for their body types.