Don't be too worried the bag label is just a generalisation , your lambs are of a small breed ( a x lamb will be 10kg + ) if they are full and content then good . Just cut out one feed then in a day or 2 cut out a second , 3 feeds per day , early morning , late evening and 1 in the middle will be fine ,they will increase amount drunk per feed . Mixing with cold water will be fine