Despite 3 attempts, my leaven never measures 60 grams. It's always about 10 grams short despite using accurate measurements. Anyone have any ideas why

So I use this recipe nearly every day and I find that it's important to make double the amount of leaven called for in the leaven recipe so that you have plenty to make your loaf. I use 30 g of starter 75 g of water and 75 g of flour to make my leaven and that usually gives me enough for two loaves (with a little left over) following this recipe. I have found that if you don't catch the leaven in time you will definitely be short. Hope this helps