How much should i give Lottie

Lottie is 11 months old now and i think she really loves her food, the problem is i dont know how much i should be giving her.
She is fed at breakfast and teatime, equal amounts of JWB dried and wet, i just put out what i think, she eats more at teatime, and sometimes leaves some of her breakfast.
She is a cross breed, terrier /german shepherd, but is more the size of a large terrier, she weighs 15 kg and looks about the right weight and is very active, should i be giving her exact amounts or shall i give what i think

If she's a healthy weight, then you're doing it right!

Has the Vet said anyhing about her weight? I wouldn't worry about what you're 'supposed' to feed as long as she's healthy and happy.