Bea is a show cocker and like Betty her breeder had her on Field and trial puppy, you do need to use the quantity's on the bag as a guide, every dog is different they may do more or less excercise and so need more or less food.
I keep an eye on Bea's waist ( far more than my own )

and while she was growing I put her on the scales monthly.
I've been told field and trial is the same ingredients as standard skinners, the only difference is that it is for " working dogs" so you don't pay the vat hence it's cheaper.