I did exactly what you did when I got my scale.....I wieghed everything. I went and got my normal mice for feeding day and it was waaaaaaaaaaayyyy over the 10 to15%. To me that percentage seems way to little so I just go by what the girth of the snake is. That works way better for both me and the snakes. I still weigh everything and document....but just dont go by the percentage. Hope that helps you.